Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1222 insertions, 0 deletions

diff --git a/third_party/aom/common/y4minput.c b/third_party/aom/common/y4minput.c
new file mode 100644
index 0000000000..1974d76f1f
--- /dev/null
+++ b/third_party/aom/common/y4minput.c
@@ -0,0 +1,1222 @@
+/*
+ * Copyright (c) 2016, Alliance for Open Media. All rights reserved
+ *
+ * This source code is subject to the terms of the BSD 2 Clause License and
+ * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+ * was not distributed with this source code in the LICENSE file, you can
+ * obtain it at www.aomedia.org/license/software. If the Alliance for Open
+ * Media Patent License 1.0 was not distributed with this source code in the
+ * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
+ *
+ * Based on code from the OggTheora software codec source code,
+ * Copyright (C) 2002-2010 The Xiph.Org Foundation and contributors.
+ */
+#include <assert.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "aom/aom_integer.h"
+#include "aom_ports/msvc.h"
+#include "y4minput.h"
+
+// Reads 'size' bytes from 'file' into 'buf' with some fault tolerance.
+// Returns true on success.
+static int file_read(void *buf, size_t size, FILE *file) {
+  const int kMaxTries = 5;
+  int try_count = 0;
+  int file_error = 0;
+  size_t len = 0;
+  while (!feof(file) && len < size && try_count < kMaxTries) {
+    const size_t n = fread((uint8_t *)buf + len, 1, size - len, file);
+    ++try_count;
+    len += n;
+    file_error = ferror(file);
+    if (file_error) {
+      if (errno == EINTR || errno == EAGAIN) {
+        clearerr(file);
+        continue;
+      } else {
+        fprintf(stderr, "Error reading file: %u of %u bytes read, %d: %s\n",
+                (uint32_t)len, (uint32_t)size, errno, strerror(errno));
+        return 0;
+      }
+    }
+  }
+
+  if (!feof(file) && len != size) {
+    fprintf(stderr,
+            "Error reading file: %u of %u bytes read,"
+            " error: %d, tries: %d, %d: %s\n",
+            (uint32_t)len, (uint32_t)size, file_error, try_count, errno,
+            strerror(errno));
+  }
+  return len == size;
+}
+
+// Stores the color range in 'y4m_ctx', returning 1 if successfully parsed,
+// 0 otherwise.
+static int parse_color_range(y4m_input *y4m_ctx, const char *buf) {
+  // Note that default is studio range.
+  if (strcmp(buf, "LIMITED") == 0) {
+    return 1;
+  }
+  if (strcmp(buf, "FULL") == 0) {
+    y4m_ctx->color_range = AOM_CR_FULL_RANGE;
+    return 1;
+  }
+  fprintf(stderr, "Unknown color range value: %s\n", buf);
+  return 0;
+}
+
+static int parse_metadata(y4m_input *y4m_ctx, const char *buf) {
+  if (strncmp(buf, "COLORRANGE=", 11) == 0) {
+    return parse_color_range(y4m_ctx, buf + 11);
+  }
+  return 1;  // No support for other metadata, just ignore them.
+}
+
+static int y4m_parse_tags(y4m_input *_y4m, char *_tags) {
+  char *p;
+  char *q;
+  for (p = _tags;; p = q) {
+    /*Skip any leading spaces.*/
+    while (*p == ' ') p++;
+    /*If that's all we have, stop.*/
+    if (p[0] == '\0') break;
+    /*Find the end of this tag.*/
+    for (q = p + 1; *q != '\0' && *q != ' '; q++) {
+    }
+    /*Process the tag.*/
+    switch (p[0]) {
+      case 'W': {
+        if (sscanf(p + 1, "%d", &_y4m->pic_w) != 1) return -1;
+      } break;
+      case 'H': {
+        if (sscanf(p + 1, "%d", &_y4m->pic_h) != 1) return -1;
+      } break;
+      case 'F': {
+        if (sscanf(p + 1, "%d:%d", &_y4m->fps_n, &_y4m->fps_d) != 2) {
+          return -1;
+        }
+      } break;
+      case 'I': {
+        _y4m->interlace = p[1];
+      } break;
+      case 'A': {
+        if (sscanf(p + 1, "%d:%d", &_y4m->par_n, &_y4m->par_d) != 2) {
+          return -1;
+        }
+      } break;
+      case 'C': {
+        if (q - p > 16) return -1;
+        memcpy(_y4m->chroma_type, p + 1, q - p - 1);
+        _y4m->chroma_type[q - p - 1] = '\0';
+      } break;
+      case 'X': {
+        if (!parse_metadata(_y4m, p + 1)) return -1;
+      } break;
+      default: break; /*Ignore unknown tags.*/
+    }
+  }
+  return 0;
+}
+
+// Copy a single tag into the buffer, along with a null character.
+// Returns 0 if any file IO errors occur.
+static int copy_tag(char *buf, size_t buf_len, char *end_tag, FILE *file) {
+  size_t i;
+  assert(buf_len >= 1);
+  // Skip leading space characters.
+  do {
+    if (!file_read(buf, 1, file)) {
+      return 0;
+    }
+  } while (buf[0] == ' ');
+
+  // If we hit the newline, treat this as the "empty" tag.
+  if (buf[0] == '\n') {
+    buf[0] = '\0';
+    *end_tag = '\n';
+    return 1;
+  }
+
+  // Copy over characters until a space is hit, or the buffer is exhausted.
+  for (i = 1; i < buf_len; ++i) {
+    if (!file_read(buf + i, 1, file)) {
+      return 0;
+    }
+    if (buf[i] == ' ' || buf[i] == '\n') {
+      break;
+    }
+  }
+  if (i == buf_len) {
+    fprintf(stderr, "Error: Y4M header tags must be less than %lu characters\n",
+            (unsigned long)i);
+    return 0;
+  }
+  *end_tag = buf[i];
+  buf[i] = '\0';
+  return 1;
+}
+
+// Returns 1 if tags were parsed successfully, 0 otherwise.
+static int parse_tags(y4m_input *y4m_ctx, FILE *file) {
+  char tag[256];
+  char end;  // Character denoting the end of the tag, ' ' or '\n'.
+  // Set Y4M tags to defaults, updating them as processing occurs. Mandatory
+  // fields are marked with -1 and will be checked after the tags are parsed.
+  y4m_ctx->pic_w = -1;
+  y4m_ctx->pic_h = -1;
+  y4m_ctx->fps_n = -1;  // Also serves as marker for fps_d
+  y4m_ctx->par_n = 0;
+  y4m_ctx->par_d = 0;
+  y4m_ctx->interlace = '?';
+  y4m_ctx->color_range = AOM_CR_STUDIO_RANGE;
+  snprintf(y4m_ctx->chroma_type, sizeof(y4m_ctx->chroma_type), "420");
+
+  // Find one tag at a time.
+  do {
+    if (!copy_tag(tag, sizeof(tag), &end, file)) {
+      return 0;
+    }
+    // y4m_parse_tags returns 0 on success.
+    if (y4m_parse_tags(y4m_ctx, tag)) {
+      return 0;
+    }
+  } while (end != '\n');
+
+  // Check the mandatory fields.
+  if (y4m_ctx->pic_w == -1) {
+    fprintf(stderr, "Width field missing\n");
+    return 0;
+  }
+  if (y4m_ctx->pic_h == -1) {
+    fprintf(stderr, "Height field missing\n");
+    return 0;
+  }
+  if (y4m_ctx->fps_n == -1) {
+    fprintf(stderr, "FPS field missing\n");
+    return 0;
+  }
+  return 1;
+}
+
+/*All anti-aliasing filters in the following conversion functions are based on
+   one of two window functions:
+  The 6-tap Lanczos window (for down-sampling and shifts):
+   sinc(\pi*t)*sinc(\pi*t/3), |t|<3  (sinc(t)==sin(t)/t)
+   0,                         |t|>=3
+  The 4-tap Mitchell window (for up-sampling):
+   7|t|^3-12|t|^2+16/3,             |t|<1
+   -(7/3)|x|^3+12|x|^2-20|x|+32/3,  |t|<2
+   0,                               |t|>=2
+  The number of taps is intentionally kept small to reduce computational
+   overhead and limit ringing.
+
+  The taps from these filters are scaled so that their sum is 1, and the
+  result is scaled by 128 and rounded to integers to create a filter whose
+   intermediate values fit inside 16 bits.
+  Coefficients are rounded in such a way as to ensure their sum is still 128,
+   which is usually equivalent to normal rounding.
+
+  Conversions which require both horizontal and vertical filtering could
+   have these steps pipelined, for less memory consumption and better cache
+   performance, but we do them separately for simplicity.*/
+#define OC_MINI(_a, _b) ((_a) > (_b) ? (_b) : (_a))
+#define OC_MAXI(_a, _b) ((_a) < (_b) ? (_b) : (_a))
+#define OC_CLAMPI(_a, _b, _c) (OC_MAXI(_a, OC_MINI(_b, _c)))
+
+/*420jpeg chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  420mpeg2 chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  BR      |       BR      |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  BR      |       BR      |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  We use a resampling filter to shift the site locations one quarter pixel (at
+   the chroma plane's resolution) to the right.
+  The 4:2:2 modes look exactly the same, except there are twice as many chroma
+   lines, and they are vertically co-sited with the luma samples in both the
+   mpeg2 and jpeg cases (thus requiring no vertical resampling).*/
+static void y4m_42xmpeg2_42xjpeg_helper(unsigned char *_dst,
+                                        const unsigned char *_src, int _c_w,
+                                        int _c_h) {
+  int y;
+  int x;
+  for (y = 0; y < _c_h; y++) {
+    /*Filter: [4 -17 114 35 -9 1]/128, derived from a 6-tap Lanczos
+       window.*/
+    for (x = 0; x < OC_MINI(_c_w, 2); x++) {
+      _dst[x] = (unsigned char)OC_CLAMPI(
+          0,
+          (4 * _src[0] - 17 * _src[OC_MAXI(x - 1, 0)] + 114 * _src[x] +
+           35 * _src[OC_MINI(x + 1, _c_w - 1)] -
+           9 * _src[OC_MINI(x + 2, _c_w - 1)] + _src[OC_MINI(x + 3, _c_w - 1)] +
+           64) >>
+              7,
+          255);
+    }
+    for (; x < _c_w - 3; x++) {
+      _dst[x] = (unsigned char)OC_CLAMPI(
+          0,
+          (4 * _src[x - 2] - 17 * _src[x - 1] + 114 * _src[x] +
+           35 * _src[x + 1] - 9 * _src[x + 2] + _src[x + 3] + 64) >>
+              7,
+          255);
+    }
+    for (; x < _c_w; x++) {
+      _dst[x] = (unsigned char)OC_CLAMPI(
+          0,
+          (4 * _src[x - 2] - 17 * _src[x - 1] + 114 * _src[x] +
+           35 * _src[OC_MINI(x + 1, _c_w - 1)] -
+           9 * _src[OC_MINI(x + 2, _c_w - 1)] + _src[_c_w - 1] + 64) >>
+              7,
+          255);
+    }
+    _dst += _c_w;
+    _src += _c_w;
+  }
+}
+
+/*This format is only used for interlaced content, but is included for
+   completeness.
+
+  420jpeg chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  420paldv chroma samples are sited like:
+  YR------Y-------YR------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YB------Y-------YB------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YR------Y-------YR------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YB------Y-------YB------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  We use a resampling filter to shift the site locations one quarter pixel (at
+   the chroma plane's resolution) to the right.
+  Then we use another filter to move the C_r location down one quarter pixel,
+   and the C_b location up one quarter pixel.*/
+static void y4m_convert_42xpaldv_42xjpeg(y4m_input *_y4m, unsigned char *_dst,
+                                         unsigned char *_aux) {
+  unsigned char *tmp;
+  int c_w;
+  int c_h;
+  int c_sz;
+  int pli;
+  int y;
+  int x;
+  /*Skip past the luma data.*/
+  _dst += _y4m->pic_w * _y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w = (_y4m->pic_w + 1) / 2;
+  c_h = (_y4m->pic_h + _y4m->dst_c_dec_h - 1) / _y4m->dst_c_dec_h;
+  c_sz = c_w * c_h;
+  tmp = _aux + 2 * c_sz;
+  for (pli = 1; pli < 3; pli++) {
+    /*First do the horizontal re-sampling.
+      This is the same as the mpeg2 case, except that after the horizontal
+       case, we need to apply a second vertical filter.*/
+    y4m_42xmpeg2_42xjpeg_helper(tmp, _aux, c_w, c_h);
+    _aux += c_sz;
+    switch (pli) {
+      case 1: {
+        /*Slide C_b up a quarter-pel.
+          This is the same filter used above, but in the other order.*/
+        for (x = 0; x < c_w; x++) {
+          for (y = 0; y < OC_MINI(c_h, 3); y++) {
+            _dst[y * c_w] = (unsigned char)OC_CLAMPI(
+                0,
+                (tmp[0] - 9 * tmp[OC_MAXI(y - 2, 0) * c_w] +
+                 35 * tmp[OC_MAXI(y - 1, 0) * c_w] + 114 * tmp[y * c_w] -
+                 17 * tmp[OC_MINI(y + 1, c_h - 1) * c_w] +
+                 4 * tmp[OC_MINI(y + 2, c_h - 1) * c_w] + 64) >>
+                    7,
+                255);
+          }
+          for (; y < c_h - 2; y++) {
+            _dst[y * c_w] = (unsigned char)OC_CLAMPI(
+                0,
+                (tmp[(y - 3) * c_w] - 9 * tmp[(y - 2) * c_w] +
+                 35 * tmp[(y - 1) * c_w] + 114 * tmp[y * c_w] -
+                 17 * tmp[(y + 1) * c_w] + 4 * tmp[(y + 2) * c_w] + 64) >>
+                    7,
+                255);
+          }
+          for (; y < c_h; y++) {
+            _dst[y * c_w] = (unsigned char)OC_CLAMPI(
+                0,
+                (tmp[(y - 3) * c_w] - 9 * tmp[(y - 2) * c_w] +
+                 35 * tmp[(y - 1) * c_w] + 114 * tmp[y * c_w] -
+                 17 * tmp[OC_MINI(y + 1, c_h - 1) * c_w] +
+                 4 * tmp[(c_h - 1) * c_w] + 64) >>
+                    7,
+                255);
+          }
+          _dst++;
+          tmp++;
+        }
+        _dst += c_sz - c_w;
+        tmp -= c_w;
+      } break;
+      case 2: {
+        /*Slide C_r down a quarter-pel.
+          This is the same as the horizontal filter.*/
+        for (x = 0; x < c_w; x++) {
+          for (y = 0; y < OC_MINI(c_h, 2); y++) {
+            _dst[y * c_w] = (unsigned char)OC_CLAMPI(
+                0,
+                (4 * tmp[0] - 17 * tmp[OC_MAXI(y - 1, 0) * c_w] +
+                 114 * tmp[y * c_w] + 35 * tmp[OC_MINI(y + 1, c_h - 1) * c_w] -
+                 9 * tmp[OC_MINI(y + 2, c_h - 1) * c_w] +
+                 tmp[OC_MINI(y + 3, c_h - 1) * c_w] + 64) >>
+                    7,
+                255);
+          }
+          for (; y < c_h - 3; y++) {
+            _dst[y * c_w] = (unsigned char)OC_CLAMPI(
+                0,
+                (4 * tmp[(y - 2) * c_w] - 17 * tmp[(y - 1) * c_w] +
+                 114 * tmp[y * c_w] + 35 * tmp[(y + 1) * c_w] -
+                 9 * tmp[(y + 2) * c_w] + tmp[(y + 3) * c_w] + 64) >>
+                    7,
+                255);
+          }
+          for (; y < c_h; y++) {
+            _dst[y * c_w] = (unsigned char)OC_CLAMPI(
+                0,
+                (4 * tmp[(y - 2) * c_w] - 17 * tmp[(y - 1) * c_w] +
+                 114 * tmp[y * c_w] + 35 * tmp[OC_MINI(y + 1, c_h - 1) * c_w] -
+                 9 * tmp[OC_MINI(y + 2, c_h - 1) * c_w] + tmp[(c_h - 1) * c_w] +
+                 64) >>
+                    7,
+                255);
+          }
+          _dst++;
+          tmp++;
+        }
+      } break;
+    }
+    /*For actual interlaced material, this would have to be done separately on
+       each field, and the shift amounts would be different.
+      C_r moves down 1/8, C_b up 3/8 in the top field, and C_r moves down 3/8,
+       C_b up 1/8 in the bottom field.
+      The corresponding filters would be:
+       Down 1/8 (reverse order for up): [3 -11 125 15 -4 0]/128
+       Down 3/8 (reverse order for up): [4 -19 98 56 -13 2]/128*/
+  }
+}
+
+/*Perform vertical filtering to reduce a single plane from 4:2:2 to 4:2:0.
+  This is used as a helper by several conversion routines.*/
+static void y4m_422jpeg_420jpeg_helper(unsigned char *_dst,
+                                       const unsigned char *_src, int _c_w,
+                                       int _c_h) {
+  int y;
+  int x;
+  /*Filter: [3 -17 78 78 -17 3]/128, derived from a 6-tap Lanczos window.*/
+  for (x = 0; x < _c_w; x++) {
+    for (y = 0; y < OC_MINI(_c_h, 2); y += 2) {
+      _dst[(y >> 1) * _c_w] =
+          OC_CLAMPI(0,
+                    (64 * _src[0] + 78 * _src[OC_MINI(1, _c_h - 1) * _c_w] -
+                     17 * _src[OC_MINI(2, _c_h - 1) * _c_w] +
+                     3 * _src[OC_MINI(3, _c_h - 1) * _c_w] + 64) >>
+                        7,
+                    255);
+    }
+    for (; y < _c_h - 3; y += 2) {
+      _dst[(y >> 1) * _c_w] =
+          OC_CLAMPI(0,
+                    (3 * (_src[(y - 2) * _c_w] + _src[(y + 3) * _c_w]) -
+                     17 * (_src[(y - 1) * _c_w] + _src[(y + 2) * _c_w]) +
+                     78 * (_src[y * _c_w] + _src[(y + 1) * _c_w]) + 64) >>
+                        7,
+                    255);
+    }
+    for (; y < _c_h; y += 2) {
+      _dst[(y >> 1) * _c_w] = OC_CLAMPI(
+          0,
+          (3 * (_src[(y - 2) * _c_w] + _src[(_c_h - 1) * _c_w]) -
+           17 * (_src[(y - 1) * _c_w] + _src[OC_MINI(y + 2, _c_h - 1) * _c_w]) +
+           78 * (_src[y * _c_w] + _src[OC_MINI(y + 1, _c_h - 1) * _c_w]) +
+           64) >>
+              7,
+          255);
+    }
+    _src++;
+    _dst++;
+  }
+}
+
+/*420jpeg chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  422jpeg chroma samples are sited like:
+  Y---BR--Y-------Y---BR--Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y---BR--Y-------Y---BR--Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y---BR--Y-------Y---BR--Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y---BR--Y-------Y---BR--Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  We use a resampling filter to decimate the chroma planes by two in the
+   vertical direction.*/
+static void y4m_convert_422jpeg_420jpeg(y4m_input *_y4m, unsigned char *_dst,
+                                        unsigned char *_aux) {
+  int c_w;
+  int c_h;
+  int c_sz;
+  int dst_c_w;
+  int dst_c_h;
+  int dst_c_sz;
+  int pli;
+  /*Skip past the luma data.*/
+  _dst += _y4m->pic_w * _y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w = (_y4m->pic_w + _y4m->src_c_dec_h - 1) / _y4m->src_c_dec_h;
+  c_h = _y4m->pic_h;
+  dst_c_w = (_y4m->pic_w + _y4m->dst_c_dec_h - 1) / _y4m->dst_c_dec_h;
+  dst_c_h = (_y4m->pic_h + _y4m->dst_c_dec_v - 1) / _y4m->dst_c_dec_v;
+  c_sz = c_w * c_h;
+  dst_c_sz = dst_c_w * dst_c_h;
+  for (pli = 1; pli < 3; pli++) {
+    y4m_422jpeg_420jpeg_helper(_dst, _aux, c_w, c_h);
+    _aux += c_sz;
+    _dst += dst_c_sz;
+  }
+}
+
+/*420jpeg chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  422 chroma samples are sited like:
+  YBR-----Y-------YBR-----Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------YBR-----Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------YBR-----Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------YBR-----Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  We use a resampling filter to shift the original site locations one quarter
+   pixel (at the original chroma resolution) to the right.
+  Then we use a second resampling filter to decimate the chroma planes by two
+   in the vertical direction.*/
+static void y4m_convert_422_420jpeg(y4m_input *_y4m, unsigned char *_dst,
+                                    unsigned char *_aux) {
+  unsigned char *tmp;
+  int c_w;
+  int c_h;
+  int c_sz;
+  int dst_c_h;
+  int dst_c_sz;
+  int pli;
+  /*Skip past the luma data.*/
+  _dst += _y4m->pic_w * _y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w = (_y4m->pic_w + _y4m->src_c_dec_h - 1) / _y4m->src_c_dec_h;
+  c_h = _y4m->pic_h;
+  dst_c_h = (_y4m->pic_h + _y4m->dst_c_dec_v - 1) / _y4m->dst_c_dec_v;
+  c_sz = c_w * c_h;
+  dst_c_sz = c_w * dst_c_h;
+  tmp = _aux + 2 * c_sz;
+  for (pli = 1; pli < 3; pli++) {
+    /*In reality, the horizontal and vertical steps could be pipelined, for
+       less memory consumption and better cache performance, but we do them
+       separately for simplicity.*/
+    /*First do horizontal filtering (convert to 422jpeg)*/
+    y4m_42xmpeg2_42xjpeg_helper(tmp, _aux, c_w, c_h);
+    /*Now do the vertical filtering.*/
+    y4m_422jpeg_420jpeg_helper(_dst, tmp, c_w, c_h);
+    _aux += c_sz;
+    _dst += dst_c_sz;
+  }
+}
+
+/*420jpeg chroma samples are sited like:
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |   BR  |       |   BR  |
+  |       |       |       |
+  Y-------Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  411 chroma samples are sited like:
+  YBR-----Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+  YBR-----Y-------Y-------Y-------
+  |       |       |       |
+  |       |       |       |
+  |       |       |       |
+
+  We use a filter to resample at site locations one eighth pixel (at the source
+   chroma plane's horizontal resolution) and five eighths of a pixel to the
+   right.
+  Then we use another filter to decimate the planes by 2 in the vertical
+   direction.*/
+static void y4m_convert_411_420jpeg(y4m_input *_y4m, unsigned char *_dst,
+                                    unsigned char *_aux) {
+  unsigned char *tmp;
+  int c_w;
+  int c_h;
+  int c_sz;
+  int dst_c_w;
+  int dst_c_h;
+  int dst_c_sz;
+  int tmp_sz;
+  int pli;
+  int y;
+  int x;
+  /*Skip past the luma data.*/
+  _dst += _y4m->pic_w * _y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w = (_y4m->pic_w + _y4m->src_c_dec_h - 1) / _y4m->src_c_dec_h;
+  c_h = _y4m->pic_h;
+  dst_c_w = (_y4m->pic_w + _y4m->dst_c_dec_h - 1) / _y4m->dst_c_dec_h;
+  dst_c_h = (_y4m->pic_h + _y4m->dst_c_dec_v - 1) / _y4m->dst_c_dec_v;
+  c_sz = c_w * c_h;
+  dst_c_sz = dst_c_w * dst_c_h;
+  tmp_sz = dst_c_w * c_h;
+  tmp = _aux + 2 * c_sz;
+  for (pli = 1; pli < 3; pli++) {
+    /*In reality, the horizontal and vertical steps could be pipelined, for
+       less memory consumption and better cache performance, but we do them
+       separately for simplicity.*/
+    /*First do horizontal filtering (convert to 422jpeg)*/
+    for (y = 0; y < c_h; y++) {
+      /*Filters: [1 110 18 -1]/128 and [-3 50 86 -5]/128, both derived from a
+         4-tap Mitchell window.*/
+      for (x = 0; x < OC_MINI(c_w, 1); x++) {
+        tmp[x << 1] = (unsigned char)OC_CLAMPI(
+            0,
+            (111 * _aux[0] + 18 * _aux[OC_MINI(1, c_w - 1)] -
+             _aux[OC_MINI(2, c_w - 1)] + 64) >>
+                7,
+            255);
+        tmp[x << 1 | 1] = (unsigned char)OC_CLAMPI(
+            0,
+            (47 * _aux[0] + 86 * _aux[OC_MINI(1, c_w - 1)] -
+             5 * _aux[OC_MINI(2, c_w - 1)] + 64) >>
+                7,
+            255);
+      }
+      for (; x < c_w - 2; x++) {
+        tmp[x << 1] =
+            (unsigned char)OC_CLAMPI(0,
+                                     (_aux[x - 1] + 110 * _aux[x] +
+                                      18 * _aux[x + 1] - _aux[x + 2] + 64) >>
+                                         7,
+                                     255);
+        tmp[x << 1 | 1] = (unsigned char)OC_CLAMPI(
+            0,
+            (-3 * _aux[x - 1] + 50 * _aux[x] + 86 * _aux[x + 1] -
+             5 * _aux[x + 2] + 64) >>
+                7,
+            255);
+      }
+      for (; x < c_w; x++) {
+        tmp[x << 1] = (unsigned char)OC_CLAMPI(
+            0,
+            (_aux[x - 1] + 110 * _aux[x] + 18 * _aux[OC_MINI(x + 1, c_w - 1)] -
+             _aux[c_w - 1] + 64) >>
+                7,
+            255);
+        if ((x << 1 | 1) < dst_c_w) {
+          tmp[x << 1 | 1] = (unsigned char)OC_CLAMPI(
+              0,
+              (-3 * _aux[x - 1] + 50 * _aux[x] +
+               86 * _aux[OC_MINI(x + 1, c_w - 1)] - 5 * _aux[c_w - 1] + 64) >>
+                  7,
+              255);
+        }
+      }
+      tmp += dst_c_w;
+      _aux += c_w;
+    }
+    tmp -= tmp_sz;
+    /*Now do the vertical filtering.*/
+    y4m_422jpeg_420jpeg_helper(_dst, tmp, dst_c_w, c_h);
+    _dst += dst_c_sz;
+  }
+}
+
+/*Convert 444 to 420jpeg.*/
+static void y4m_convert_444_420jpeg(y4m_input *_y4m, unsigned char *_dst,
+                                    unsigned char *_aux) {
+  unsigned char *tmp;
+  int c_w;
+  int c_h;
+  int c_sz;
+  int dst_c_w;
+  int dst_c_h;
+  int dst_c_sz;
+  int tmp_sz;
+  int pli;
+  int y;
+  int x;
+  /*Skip past the luma data.*/
+  _dst += _y4m->pic_w * _y4m->pic_h;
+  /*Compute the size of each chroma plane.*/
+  c_w = (_y4m->pic_w + _y4m->src_c_dec_h - 1) / _y4m->src_c_dec_h;
+  c_h = _y4m->pic_h;
+  dst_c_w = (_y4m->pic_w + _y4m->dst_c_dec_h - 1) / _y4m->dst_c_dec_h;
+  dst_c_h = (_y4m->pic_h + _y4m->dst_c_dec_v - 1) / _y4m->dst_c_dec_v;
+  c_sz = c_w * c_h;
+  dst_c_sz = dst_c_w * dst_c_h;
+  tmp_sz = dst_c_w * c_h;
+  tmp = _aux + 2 * c_sz;
+  for (pli = 1; pli < 3; pli++) {
+    /*Filter: [3 -17 78 78 -17 3]/128, derived from a 6-tap Lanczos window.*/
+    for (y = 0; y < c_h; y++) {
+      for (x = 0; x < OC_MINI(c_w, 2); x += 2) {
+        tmp[x >> 1] = OC_CLAMPI(0,
+                                (64 * _aux[0] + 78 * _aux[OC_MINI(1, c_w - 1)] -
+                                 17 * _aux[OC_MINI(2, c_w - 1)] +
+                                 3 * _aux[OC_MINI(3, c_w - 1)] + 64) >>
+                                    7,
+                                255);
+      }
+      for (; x < c_w - 3; x += 2) {
+        tmp[x >> 1] = OC_CLAMPI(0,
+                                (3 * (_aux[x - 2] + _aux[x + 3]) -
+                                 17 * (_aux[x - 1] + _aux[x + 2]) +
+                                 78 * (_aux[x] + _aux[x + 1]) + 64) >>
+                                    7,
+                                255);
+      }
+      for (; x < c_w; x += 2) {
+        tmp[x >> 1] =
+            OC_CLAMPI(0,
+                      (3 * (_aux[x - 2] + _aux[c_w - 1]) -
+                       17 * (_aux[x - 1] + _aux[OC_MINI(x + 2, c_w - 1)]) +
+                       78 * (_aux[x] + _aux[OC_MINI(x + 1, c_w - 1)]) + 64) >>
+                          7,
+                      255);
+      }
+      tmp += dst_c_w;
+      _aux += c_w;
+    }
+    tmp -= tmp_sz;
+    /*Now do the vertical filtering.*/
+    y4m_422jpeg_420jpeg_helper(_dst, tmp, dst_c_w, c_h);
+    _dst += dst_c_sz;
+  }
+}
+
+/*The image is padded with empty chroma components at 4:2:0.*/
+static void y4m_convert_mono_420jpeg(y4m_input *_y4m, unsigned char *_dst,
+                                     unsigned char *_aux) {
+  int c_sz;
+  (void)_aux;
+  _dst += _y4m->pic_w * _y4m->pic_h;
+  c_sz = ((_y4m->pic_w + _y4m->dst_c_dec_h - 1) / _y4m->dst_c_dec_h) *
+         ((_y4m->pic_h + _y4m->dst_c_dec_v - 1) / _y4m->dst_c_dec_v);
+  memset(_dst, 128, c_sz * 2);
+}
+
+/*No conversion function needed.*/
+static void y4m_convert_null(y4m_input *_y4m, unsigned char *_dst,
+                             unsigned char *_aux) {
+  (void)_y4m;
+  (void)_dst;
+  (void)_aux;
+}
+
+static const char TAG[] = "YUV4MPEG2";
+
+int y4m_input_open(y4m_input *y4m_ctx, FILE *file, char *skip_buffer,
+                   int num_skip, aom_chroma_sample_position_t csp,
+                   int only_420) {
+  // File must start with |TAG|.
+  char tag_buffer[9];  // 9 == strlen(TAG)
+  // Read as much as possible from |skip_buffer|, which were characters
+  // that were previously read from the file to do input-type detection.
+  assert(num_skip >= 0 && num_skip <= 8);
+  if (num_skip > 0) {
+    memcpy(tag_buffer, skip_buffer, num_skip);
+  }
+  // Start reading from the file now that the |skip_buffer| is depleted.
+  if (!file_read(tag_buffer + num_skip, 9 - num_skip, file)) {
+    return -1;
+  }
+  if (memcmp(TAG, tag_buffer, 9) != 0) {
+    fprintf(stderr, "Error parsing header: must start with %s\n", TAG);
+    return -1;
+  }
+  // Next character must be a space.
+  if (!file_read(tag_buffer, 1, file) || tag_buffer[0] != ' ') {
+    fprintf(stderr, "Error parsing header: space must follow %s\n", TAG);
+    return -1;
+  }
+  if (!parse_tags(y4m_ctx, file)) {
+    fprintf(stderr, "Error parsing %s header.\n", TAG);
+    return -1;
+  }
+  if (y4m_ctx->interlace == '?') {
+    fprintf(stderr,
+            "Warning: Input video interlacing format unknown; "
+            "assuming progressive scan.\n");
+  } else if (y4m_ctx->interlace != 'p') {
+    fprintf(stderr,
+            "Input video is interlaced; "
+            "Only progressive scan handled.\n");
+    return -1;
+  }
+  /* Only support vertical chroma sample position if the input format is
+   * already 420mpeg2. Colocated is not supported in Y4M.
+   */
+  if (csp == AOM_CSP_VERTICAL &&
+      strcmp(y4m_ctx->chroma_type, "420mpeg2") != 0) {
+    fprintf(stderr,
+            "Vertical chroma sample position only supported "
+            "for 420mpeg2 input\n");
+    return -1;
+  }
+  if (csp == AOM_CSP_COLOCATED) {
+    // TODO(any): check the right way to handle this in y4m
+    fprintf(stderr,
+            "Ignoring colocated chroma sample position for reading in Y4M\n");
+  }
+  y4m_ctx->aom_fmt = AOM_IMG_FMT_I420;
+  y4m_ctx->bps = 12;
+  y4m_ctx->bit_depth = 8;
+  y4m_ctx->aux_buf = NULL;
+  y4m_ctx->dst_buf = NULL;
+  if (strcmp(y4m_ctx->chroma_type, "420") == 0 ||
+      strcmp(y4m_ctx->chroma_type, "420jpeg") == 0 ||
+      strcmp(y4m_ctx->chroma_type, "420mpeg2") == 0) {
+    y4m_ctx->src_c_dec_h = y4m_ctx->dst_c_dec_h = y4m_ctx->src_c_dec_v =
+        y4m_ctx->dst_c_dec_v = 2;
+    y4m_ctx->dst_buf_read_sz =
+        y4m_ctx->pic_w * y4m_ctx->pic_h +
+        2 * ((y4m_ctx->pic_w + 1) / 2) * ((y4m_ctx->pic_h + 1) / 2);
+    /* Natively supported: no conversion required. */
+    y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz = 0;
+    y4m_ctx->convert = y4m_convert_null;
+  } else if (strcmp(y4m_ctx->chroma_type, "420p10") == 0) {
+    y4m_ctx->src_c_dec_h = 2;
+    y4m_ctx->dst_c_dec_h = 2;
+    y4m_ctx->src_c_dec_v = 2;
+    y4m_ctx->dst_c_dec_v = 2;
+    y4m_ctx->dst_buf_read_sz =
+        2 * (y4m_ctx->pic_w * y4m_ctx->pic_h +
+             2 * ((y4m_ctx->pic_w + 1) / 2) * ((y4m_ctx->pic_h + 1) / 2));
+    /* Natively supported: no conversion required. */
+    y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz = 0;
+    y4m_ctx->convert = y4m_convert_null;
+    y4m_ctx->bit_depth = 10;
+    y4m_ctx->bps = 15;
+    y4m_ctx->aom_fmt = AOM_IMG_FMT_I42016;
+    if (only_420) {
+      fprintf(stderr, "Unsupported conversion from 420p10 to 420jpeg\n");
+      return -1;
+    }
+  } else if (strcmp(y4m_ctx->chroma_type, "420p12") == 0) {
+    y4m_ctx->src_c_dec_h = 2;
+    y4m_ctx->dst_c_dec_h = 2;
+    y4m_ctx->src_c_dec_v = 2;
+    y4m_ctx->dst_c_dec_v = 2;
+    y4m_ctx->dst_buf_read_sz =
+        2 * (y4m_ctx->pic_w * y4m_ctx->pic_h +
+             2 * ((y4m_ctx->pic_w + 1) / 2) * ((y4m_ctx->pic_h + 1) / 2));
+    /* Natively supported: no conversion required. */
+    y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz = 0;
+    y4m_ctx->convert = y4m_convert_null;
+    y4m_ctx->bit_depth = 12;
+    y4m_ctx->bps = 18;
+    y4m_ctx->aom_fmt = AOM_IMG_FMT_I42016;
+    if (only_420) {
+      fprintf(stderr, "Unsupported conversion from 420p12 to 420jpeg\n");
+      return -1;
+    }
+  } else if (strcmp(y4m_ctx->chroma_type, "420paldv") == 0) {
+    y4m_ctx->src_c_dec_h = y4m_ctx->dst_c_dec_h = y4m_ctx->src_c_dec_v =
+        y4m_ctx->dst_c_dec_v = 2;
+    y4m_ctx->dst_buf_read_sz = y4m_ctx->pic_w * y4m_ctx->pic_h;
+    /*Chroma filter required: read into the aux buf first.
+      We need to make two filter passes, so we need some extra space in the
+       aux buffer.*/
+    y4m_ctx->aux_buf_sz =
+        3 * ((y4m_ctx->pic_w + 1) / 2) * ((y4m_ctx->pic_h + 1) / 2);
+    y4m_ctx->aux_buf_read_sz =
+        2 * ((y4m_ctx->pic_w + 1) / 2) * ((y4m_ctx->pic_h + 1) / 2);
+    y4m_ctx->convert = y4m_convert_42xpaldv_42xjpeg;
+  } else if (strcmp(y4m_ctx->chroma_type, "422jpeg") == 0) {
+    y4m_ctx->src_c_dec_h = y4m_ctx->dst_c_dec_h = 2;
+    y4m_ctx->src_c_dec_v = 1;
+    y4m_ctx->dst_c_dec_v = 2;
+    y4m_ctx->dst_buf_read_sz = y4m_ctx->pic_w * y4m_ctx->pic_h;
+    /*Chroma filter required: read into the aux buf first.*/
+    y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz =
+        2 * ((y4m_ctx->pic_w + 1) / 2) * y4m_ctx->pic_h;
+    y4m_ctx->convert = y4m_convert_422jpeg_420jpeg;
+  } else if (strcmp(y4m_ctx->chroma_type, "422") == 0) {
+    y4m_ctx->src_c_dec_h = 2;
+    y4m_ctx->src_c_dec_v = 1;
+    if (only_420) {
+      y4m_ctx->dst_c_dec_h = 2;
+      y4m_ctx->dst_c_dec_v = 2;
+      y4m_ctx->dst_buf_read_sz = y4m_ctx->pic_w * y4m_ctx->pic_h;
+      /*Chroma filter required: read into the aux buf first.
+        We need to make two filter passes, so we need some extra space in the
+         aux buffer.*/
+      y4m_ctx->aux_buf_read_sz =
+          2 * ((y4m_ctx->pic_w + 1) / 2) * y4m_ctx->pic_h;
+      y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz +
+                            ((y4m_ctx->pic_w + 1) / 2) * y4m_ctx->pic_h;
+      y4m_ctx->convert = y4m_convert_422_420jpeg;
+    } else {
+      y4m_ctx->aom_fmt = AOM_IMG_FMT_I422;
+      y4m_ctx->bps = 16;
+      y4m_ctx->dst_c_dec_h = y4m_ctx->src_c_dec_h;
+      y4m_ctx->dst_c_dec_v = y4m_ctx->src_c_dec_v;
+      y4m_ctx->dst_buf_read_sz =
+          y4m_ctx->pic_w * y4m_ctx->pic_h +
+          2 * ((y4m_ctx->pic_w + 1) / 2) * y4m_ctx->pic_h;
+      /*Natively supported: no conversion required.*/
+      y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz = 0;
+      y4m_ctx->convert = y4m_convert_null;
+    }
+  } else if (strcmp(y4m_ctx->chroma_type, "422p10") == 0) {
+    y4m_ctx->src_c_dec_h = 2;
+    y4m_ctx->src_c_dec_v = 1;
+    y4m_ctx->aom_fmt = AOM_IMG_FMT_I42216;
+    y4m_ctx->bps = 20;
+    y4m_ctx->bit_depth = 10;
+    y4m_ctx->dst_c_dec_h = y4m_ctx->src_c_dec_h;
+    y4m_ctx->dst_c_dec_v = y4m_ctx->src_c_dec_v;
+    y4m_ctx->dst_buf_read_sz =
+        2 * (y4m_ctx->pic_w * y4m_ctx->pic_h +
+             2 * ((y4m_ctx->pic_w + 1) / 2) * y4m_ctx->pic_h);
+    y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz = 0;
+    y4m_ctx->convert = y4m_convert_null;
+    if (only_420) {
+      fprintf(stderr, "Unsupported conversion from 422p10 to 420jpeg\n");
+      return -1;
+    }
+  } else if (strcmp(y4m_ctx->chroma_type, "422p12") == 0) {
+    y4m_ctx->src_c_dec_h = 2;
+    y4m_ctx->src_c_dec_v = 1;
+    y4m_ctx->aom_fmt = AOM_IMG_FMT_I42216;
+    y4m_ctx->bps = 24;
+    y4m_ctx->bit_depth = 12;
+    y4m_ctx->dst_c_dec_h = y4m_ctx->src_c_dec_h;
+    y4m_ctx->dst_c_dec_v = y4m_ctx->src_c_dec_v;
+    y4m_ctx->dst_buf_read_sz =
+        2 * (y4m_ctx->pic_w * y4m_ctx->pic_h +
+             2 * ((y4m_ctx->pic_w + 1) / 2) * y4m_ctx->pic_h);
+    y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz = 0;
+    y4m_ctx->convert = y4m_convert_null;
+    if (only_420) {
+      fprintf(stderr, "Unsupported conversion from 422p12 to 420jpeg\n");
+      return -1;
+    }
+  } else if (strcmp(y4m_ctx->chroma_type, "411") == 0) {
+    y4m_ctx->src_c_dec_h = 4;
+    y4m_ctx->dst_c_dec_h = 2;
+    y4m_ctx->src_c_dec_v = 1;
+    y4m_ctx->dst_c_dec_v = 2;
+    y4m_ctx->dst_buf_read_sz = y4m_ctx->pic_w * y4m_ctx->pic_h;
+    /*Chroma filter required: read into the aux buf first.
+      We need to make two filter passes, so we need some extra space in the
+       aux buffer.*/
+    y4m_ctx->aux_buf_read_sz = 2 * ((y4m_ctx->pic_w + 3) / 4) * y4m_ctx->pic_h;
+    y4m_ctx->aux_buf_sz =
+        y4m_ctx->aux_buf_read_sz + ((y4m_ctx->pic_w + 1) / 2) * y4m_ctx->pic_h;
+    y4m_ctx->convert = y4m_convert_411_420jpeg;
+  } else if (strcmp(y4m_ctx->chroma_type, "444") == 0) {
+    y4m_ctx->src_c_dec_h = 1;
+    y4m_ctx->src_c_dec_v = 1;
+    if (only_420) {
+      y4m_ctx->dst_c_dec_h = 2;
+      y4m_ctx->dst_c_dec_v = 2;
+      y4m_ctx->dst_buf_read_sz = y4m_ctx->pic_w * y4m_ctx->pic_h;
+      /*Chroma filter required: read into the aux buf first.
+        We need to make two filter passes, so we need some extra space in the
+         aux buffer.*/
+      y4m_ctx->aux_buf_read_sz = 2 * y4m_ctx->pic_w * y4m_ctx->pic_h;
+      y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz +
+                            ((y4m_ctx->pic_w + 1) / 2) * y4m_ctx->pic_h;
+      y4m_ctx->convert = y4m_convert_444_420jpeg;
+    } else {
+      y4m_ctx->aom_fmt = AOM_IMG_FMT_I444;
+      y4m_ctx->bps = 24;
+      y4m_ctx->dst_c_dec_h = y4m_ctx->src_c_dec_h;
+      y4m_ctx->dst_c_dec_v = y4m_ctx->src_c_dec_v;
+      y4m_ctx->dst_buf_read_sz = 3 * y4m_ctx->pic_w * y4m_ctx->pic_h;
+      /*Natively supported: no conversion required.*/
+      y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz = 0;
+      y4m_ctx->convert = y4m_convert_null;
+    }
+  } else if (strcmp(y4m_ctx->chroma_type, "444p10") == 0) {
+    y4m_ctx->src_c_dec_h = 1;
+    y4m_ctx->src_c_dec_v = 1;
+    y4m_ctx->aom_fmt = AOM_IMG_FMT_I44416;
+    y4m_ctx->bps = 30;
+    y4m_ctx->bit_depth = 10;
+    y4m_ctx->dst_c_dec_h = y4m_ctx->src_c_dec_h;
+    y4m_ctx->dst_c_dec_v = y4m_ctx->src_c_dec_v;
+    y4m_ctx->dst_buf_read_sz = 2 * 3 * y4m_ctx->pic_w * y4m_ctx->pic_h;
+    y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz = 0;
+    y4m_ctx->convert = y4m_convert_null;
+    if (only_420) {
+      fprintf(stderr, "Unsupported conversion from 444p10 to 420jpeg\n");
+      return -1;
+    }
+  } else if (strcmp(y4m_ctx->chroma_type, "444p12") == 0) {
+    y4m_ctx->src_c_dec_h = 1;
+    y4m_ctx->src_c_dec_v = 1;
+    y4m_ctx->aom_fmt = AOM_IMG_FMT_I44416;
+    y4m_ctx->bps = 36;
+    y4m_ctx->bit_depth = 12;
+    y4m_ctx->dst_c_dec_h = y4m_ctx->src_c_dec_h;
+    y4m_ctx->dst_c_dec_v = y4m_ctx->src_c_dec_v;
+    y4m_ctx->dst_buf_read_sz = 2 * 3 * y4m_ctx->pic_w * y4m_ctx->pic_h;
+    y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz = 0;
+    y4m_ctx->convert = y4m_convert_null;
+    if (only_420) {
+      fprintf(stderr, "Unsupported conversion from 444p12 to 420jpeg\n");
+      return -1;
+    }
+  } else if (strcmp(y4m_ctx->chroma_type, "444alpha") == 0) {
+    y4m_ctx->src_c_dec_h = 1;
+    y4m_ctx->src_c_dec_v = 1;
+    if (only_420) {
+      y4m_ctx->dst_c_dec_h = 2;
+      y4m_ctx->dst_c_dec_v = 2;
+      y4m_ctx->dst_buf_read_sz = y4m_ctx->pic_w * y4m_ctx->pic_h;
+      /*Chroma filter required: read into the aux buf first.
+        We need to make two filter passes, so we need some extra space in the
+         aux buffer.
+        The extra plane also gets read into the aux buf.
+        It will be discarded.*/
+      y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz =
+          3 * y4m_ctx->pic_w * y4m_ctx->pic_h;
+      y4m_ctx->convert = y4m_convert_444_420jpeg;
+    } else {
+      fprintf(stderr, "Unsupported format: 444A\n");
+      return -1;
+    }
+  } else if (strcmp(y4m_ctx->chroma_type, "mono") == 0) {
+    y4m_ctx->src_c_dec_h = y4m_ctx->src_c_dec_v = 0;
+    y4m_ctx->dst_c_dec_h = y4m_ctx->dst_c_dec_v = 2;
+    y4m_ctx->dst_buf_read_sz = y4m_ctx->pic_w * y4m_ctx->pic_h;
+    /*No extra space required, but we need to clear the chroma planes.*/
+    y4m_ctx->aux_buf_sz = y4m_ctx->aux_buf_read_sz = 0;
+    y4m_ctx->convert = y4m_convert_mono_420jpeg;
+  } else {
+    fprintf(stderr, "Unknown chroma sampling type: %s\n", y4m_ctx->chroma_type);
+    return -1;
+  }
+  /*The size of the final frame buffers is always computed from the
+     destination chroma decimation type.*/
+  y4m_ctx->dst_buf_sz =
+      y4m_ctx->pic_w * y4m_ctx->pic_h +
+      2 * ((y4m_ctx->pic_w + y4m_ctx->dst_c_dec_h - 1) / y4m_ctx->dst_c_dec_h) *
+          ((y4m_ctx->pic_h + y4m_ctx->dst_c_dec_v - 1) / y4m_ctx->dst_c_dec_v);
+  if (y4m_ctx->bit_depth == 8)
+    y4m_ctx->dst_buf = (unsigned char *)malloc(y4m_ctx->dst_buf_sz);
+  else
+    y4m_ctx->dst_buf = (unsigned char *)malloc(2 * y4m_ctx->dst_buf_sz);
+  if (!y4m_ctx->dst_buf) return -1;
+
+  if (y4m_ctx->aux_buf_sz > 0) {
+    y4m_ctx->aux_buf = (unsigned char *)malloc(y4m_ctx->aux_buf_sz);
+    if (!y4m_ctx->aux_buf) {
+      free(y4m_ctx->dst_buf);
+      return -1;
+    }
+  }
+  return 0;
+}
+
+void y4m_input_close(y4m_input *_y4m) {
+  free(_y4m->dst_buf);
+  free(_y4m->aux_buf);
+}
+
+int y4m_input_fetch_frame(y4m_input *_y4m, FILE *_fin, aom_image_t *_img) {
+  char frame[6];
+  int pic_sz;
+  int c_w;
+  int c_h;
+  int c_sz;
+  int bytes_per_sample = _y4m->bit_depth > 8 ? 2 : 1;
+  /*Read and skip the frame header.*/
+  if (!file_read(frame, 6, _fin)) return 0;
+  if (memcmp(frame, "FRAME", 5)) {
+    fprintf(stderr, "Loss of framing in Y4M input data\n");
+    return -1;
+  }
+  if (frame[5] != '\n') {
+    char c;
+    int j;
+    for (j = 0; j < 79 && file_read(&c, 1, _fin) && c != '\n'; j++) {
+    }
+    if (j == 79) {
+      fprintf(stderr, "Error parsing Y4M frame header\n");
+      return -1;
+    }
+  }
+  /*Read the frame data that needs no conversion.*/
+  if (!file_read(_y4m->dst_buf, _y4m->dst_buf_read_sz, _fin)) {
+    fprintf(stderr, "Error reading Y4M frame data.\n");
+    return -1;
+  }
+  /*Read the frame data that does need conversion.*/
+  if (!file_read(_y4m->aux_buf, _y4m->aux_buf_read_sz, _fin)) {
+    fprintf(stderr, "Error reading Y4M frame data.\n");
+    return -1;
+  }
+  /*Now convert the just read frame.*/
+  (*_y4m->convert)(_y4m, _y4m->dst_buf, _y4m->aux_buf);
+  /*Fill in the frame buffer pointers.
+    We don't use aom_img_wrap() because it forces padding for odd picture
+     sizes, which would require a separate fread call for every row.*/
+  memset(_img, 0, sizeof(*_img));
+  /*Y4M has the planes in Y'CbCr order, which libaom calls Y, U, and V.*/
+  _img->fmt = _y4m->aom_fmt;
+  _img->w = _img->d_w = _y4m->pic_w;
+  _img->h = _img->d_h = _y4m->pic_h;
+  _img->bit_depth = _y4m->bit_depth;
+  _img->x_chroma_shift = _y4m->dst_c_dec_h >> 1;
+  _img->y_chroma_shift = _y4m->dst_c_dec_v >> 1;
+  _img->bps = _y4m->bps;
+
+  /*Set up the buffer pointers.*/
+  pic_sz = _y4m->pic_w * _y4m->pic_h * bytes_per_sample;
+  c_w = (_y4m->pic_w + _y4m->dst_c_dec_h - 1) / _y4m->dst_c_dec_h;
+  c_w *= bytes_per_sample;
+  c_h = (_y4m->pic_h + _y4m->dst_c_dec_v - 1) / _y4m->dst_c_dec_v;
+  c_sz = c_w * c_h;
+  _img->stride[AOM_PLANE_Y] = _y4m->pic_w * bytes_per_sample;
+  _img->stride[AOM_PLANE_U] = _img->stride[AOM_PLANE_V] = c_w;
+  _img->planes[AOM_PLANE_Y] = _y4m->dst_buf;
+  _img->planes[AOM_PLANE_U] = _y4m->dst_buf + pic_sz;
+  _img->planes[AOM_PLANE_V] = _y4m->dst_buf + pic_sz + c_sz;
+  return 1;
+}