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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 17:32:43 +0000 |
commit | 6bf0a5cb5034a7e684dcc3500e841785237ce2dd (patch) | |
tree | a68f146d7fa01f0134297619fbe7e33db084e0aa /third_party/libwebrtc/test/pc/e2e/g3doc/architecture.md | |
parent | Initial commit. (diff) | |
download | thunderbird-6bf0a5cb5034a7e684dcc3500e841785237ce2dd.tar.xz thunderbird-6bf0a5cb5034a7e684dcc3500e841785237ce2dd.zip |
Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | third_party/libwebrtc/test/pc/e2e/g3doc/architecture.md | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/third_party/libwebrtc/test/pc/e2e/g3doc/architecture.md b/third_party/libwebrtc/test/pc/e2e/g3doc/architecture.md new file mode 100644 index 0000000000..1b68c6db2c --- /dev/null +++ b/third_party/libwebrtc/test/pc/e2e/g3doc/architecture.md @@ -0,0 +1,209 @@ +<!-- go/cmark --> +<!--* freshness: {owner: 'titovartem' reviewed: '2021-04-12'} *--> + +# PeerConnection level framework fixture architecture + +## Overview + +The main implementation of +[`webrtc::webrtc_pc_e2e::PeerConnectionE2EQualityTestFixture`][1] is +[`webrtc::webrtc_pc_e2e::PeerConnectionE2EQualityTest`][2]. Internally it owns +the next main pieces: + +* [`MediaHelper`][3] - responsible for adding audio and video tracks to the + peers. +* [`VideoQualityAnalyzerInjectionHelper`][4] and + [`SingleProcessEncodedImageDataInjector`][5] - used to inject video quality + analysis and properly match captured and rendered video frames. You can read + more about it in + [DefaultVideoQualityAnalyzer](default_video_quality_analyzer.md) section. +* [`AudioQualityAnalyzerInterface`][6] - used to measure audio quality metrics +* [`TestActivitiesExecutor`][7] - used to support [`ExecuteAt(...)`][8] and + [`ExecuteEvery(...)`][9] API of `PeerConnectionE2EQualityTestFixture` to run + any arbitrary action during test execution timely synchronized with a test + call. +* A vector of [`QualityMetricsReporter`][10] added by the + `PeerConnectionE2EQualityTestFixture` user. +* Two peers: Alice and Bob represented by instances of [`TestPeer`][11] + object. + +Also it keeps a reference to [`webrtc::TimeController`][12], which is used to +create all required threads, task queues, task queue factories and time related +objects. + +## TestPeer + +Call participants are represented by instances of `TestPeer` object. +[`TestPeerFactory`][13] is used to create them. `TestPeer` owns all instances +related to the `webrtc::PeerConnection`, including required listeners and +callbacks. Also it provides an API to do offer/answer exchange and ICE candidate +exchange. For this purposes internally it uses an instance of +[`webrtc::PeerConnectionWrapper`][14]. + +The `TestPeer` also owns the `PeerConnection` worker thread. The signaling +thread for all `PeerConnection`'s is owned by +`PeerConnectionE2EQualityTestFixture` and shared between all participants in the +call. The network thread is owned by the network layer (it maybe either emulated +network provided by [Network Emulation Framework][24] or network thread and +`rtc::NetworkManager` provided by user) and provided when peer is added to the +fixture via [`AddPeer(...)`][15] API. + +## GetStats API based metrics reporters + +`PeerConnectionE2EQualityTestFixture` gives the user ability to provide +different `QualityMetricsReporter`s which will listen for `PeerConnection` +[`GetStats`][16] API. Then such reporters will be able to report various metrics +that user wants to measure. + +`PeerConnectionE2EQualityTestFixture` itself also uses this mechanism to +measure: + +* Audio quality metrics +* Audio/Video sync metrics (with help of [`CrossMediaMetricsReporter`][17]) + +Also framework provides a [`StatsBasedNetworkQualityMetricsReporter`][18] to +measure network related WebRTC metrics and print debug raw emulated network +statistic. This reporter should be added by user via +[`AddQualityMetricsReporter(...)`][19] API if requried. + +Internally stats gathering is done by [`StatsPoller`][20]. Stats are requested +once per second for each `PeerConnection` and then resulted object is provided +into each stats listener. + +## Offer/Answer exchange + +`PeerConnectionE2EQualityTest` provides ability to test Simulcast and SVC for +video. These features aren't supported by P2P call and in general requires a +Selective Forwarding Unit (SFU). So special logic is applied to mimic SFU +behavior in P2P call. This logic is located inside [`SignalingInterceptor`][21], +[`QualityAnalyzingVideoEncoder`][22] and [`QualityAnalyzingVideoDecoder`][23] +and consist of SDP modification during offer/answer exchange and special +handling of video frames from unrelated Simulcast/SVC streams during decoding. + +### Simulcast + +In case of Simulcast we have a video track, which internally contains multiple +video streams, for example low resolution, medium resolution and high +resolution. WebRTC client doesn't support receiving an offer with multiple +streams in it, because usually SFU will keep only single stream for the client. +To bypass it framework will modify offer by converting a single track with three +video streams into three independent video tracks. Then sender will think that +it send simulcast, but receiver will think that it receives 3 independent +tracks. + +To achieve such behavior some extra tweaks are required: + +* MID RTP header extension from original offer have to be removed +* RID RTP header extension from original offer is replaced with MID RTP header + extension, so the ID that sender uses for RID on receiver will be parsed as + MID. +* Answer have to be modified in the opposite way. + +Described modifications are illustrated on the picture below. + +![VP8 Simulcast offer modification](vp8_simulcast_offer_modification.png "VP8 Simulcast offer modification") + +The exchange will look like this: + +1. Alice creates an offer +2. Alice sets offer as local description +3. Do described offer modification +4. Alice sends modified offer to Bob +5. Bob sets modified offer as remote description +6. Bob creates answer +7. Bob sets answer as local description +8. Do reverse modifications on answer +9. Bob sends modified answer to Alice +10. Alice sets modified answer as remote description + +Such mechanism put a constraint that RTX streams are not supported, because they +don't have RID RTP header extension in their packets. + +### SVC + +In case of SVC the framework will update the sender's offer before even setting +it as local description on the sender side. Then no changes to answer will be +required. + +`ssrc` is a 32 bit random value that is generated in RTP to denote a specific +source used to send media in an RTP connection. In original offer video track +section will look like this: + +``` +m=video 9 UDP/TLS/RTP/SAVPF 98 100 99 101 +... +a=ssrc-group:FID <primary ssrc> <retransmission ssrc> +a=ssrc:<primary ssrc> cname:... +.... +a=ssrc:<retransmission ssrc> cname:... +.... +``` + +To enable SVC for such video track framework will add extra `ssrc`s for each SVC +stream that is required like this: + +``` +a=ssrc-group:FID <Low resolution primary ssrc> <Low resolution retransmission ssrc> +a=ssrc:<Low resolution primary ssrc> cname:... +.... +a=ssrc:<Low resolution retransmission ssrc> cname:.... +... +a=ssrc-group:FID <Medium resolution primary ssrc> <Medium resolution retransmission ssrc> +a=ssrc:<Medium resolution primary ssrc> cname:... +.... +a=ssrc:<Medium resolution retransmission ssrc> cname:.... +... +a=ssrc-group:FID <High resolution primary ssrc> <High resolution retransmission ssrc> +a=ssrc:<High resolution primary ssrc> cname:... +.... +a=ssrc:<High resolution retransmission ssrc> cname:.... +... +``` + +The next line will also be added to the video track section of the offer: + +``` +a=ssrc-group:SIM <Low resolution primary ssrc> <Medium resolution primary ssrc> <High resolution primary ssrc> +``` + +It will tell PeerConnection that this track should be configured as SVC. It +utilize WebRTC Plan B offer structure to achieve SVC behavior, also it modifies +offer before setting it as local description which violates WebRTC standard. +Also it adds limitations that on lossy networks only top resolution streams can +be analyzed, because WebRTC won't try to restore low resolution streams in case +of loss, because it still receives higher stream. + +### Handling in encoder/decoder + +In the encoder, the framework for each encoded video frame will propagate +information requried for the fake SFU to know if it belongs to an interesting +simulcast stream/spatial layer of if it should be "discarded". + +On the decoder side frames that should be "discarded" by fake SFU will be auto +decoded into single pixel images and only the interesting simulcast +stream/spatial layer will go into real decoder and then will be analyzed. + +[1]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/api/test/peerconnection_quality_test_fixture.h;l=55;drc=484acf27231d931dbc99aedce85bc27e06486b96 +[2]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/peer_connection_quality_test.h;l=44;drc=6cc893ad778a0965e2b7a8e614f3c98aa81bee5b +[3]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/media/media_helper.h;l=27;drc=d46db9f1523ae45909b4a6fdc90a140443068bc6 +[4]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/analyzer/video/video_quality_analyzer_injection_helper.h;l=38;drc=79020414fd5c71f9ec1f25445ea5f1c8001e1a49 +[5]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/analyzer/video/single_process_encoded_image_data_injector.h;l=40;drc=79020414fd5c71f9ec1f25445ea5f1c8001e1a49 +[6]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/api/test/audio_quality_analyzer_interface.h;l=23;drc=20f45823e37fd7272aa841831c029c21f29742c2 +[7]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/test_activities_executor.h;l=28;drc=6cc893ad778a0965e2b7a8e614f3c98aa81bee5b +[8]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/api/test/peerconnection_quality_test_fixture.h;l=439;drc=484acf27231d931dbc99aedce85bc27e06486b96 +[9]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/api/test/peerconnection_quality_test_fixture.h;l=445;drc=484acf27231d931dbc99aedce85bc27e06486b96 +[10]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/api/test/peerconnection_quality_test_fixture.h;l=413;drc=9438fb3fff97c803d1ead34c0e4f223db168526f +[11]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/test_activities_executor.h;l=28;drc=6cc893ad778a0965e2b7a8e614f3c98aa81bee5b +[12]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/test_activities_executor.h;l=28;drc=6cc893ad778a0965e2b7a8e614f3c98aa81bee5b +[13]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/test_peer_factory.h;l=46;drc=0ef4a2488a466a24ab97b31fdddde55440d451f9 +[14]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/pc/peer_connection_wrapper.h;l=47;drc=5ab79e62f691875a237ea28ca3975ea1f0ed62ec +[15]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/api/test/peerconnection_quality_test_fixture.h;l=459;drc=484acf27231d931dbc99aedce85bc27e06486b96 +[16]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/api/peer_connection_interface.h;l=886;drc=9438fb3fff97c803d1ead34c0e4f223db168526f +[17]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/cross_media_metrics_reporter.h;l=29;drc=9d777620236ec76754cfce19f6e82dd18e52d22c +[18]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/cross_media_metrics_reporter.h;l=29;drc=9d777620236ec76754cfce19f6e82dd18e52d22c +[19]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/api/test/peerconnection_quality_test_fixture.h;l=450;drc=484acf27231d931dbc99aedce85bc27e06486b96 +[20]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/stats_poller.h;l=52;drc=9b526180c9e9722d3fc7f8689da6ec094fc7fc0a +[21]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/sdp/sdp_changer.h;l=79;drc=ee558dcca89fd8b105114ededf9e74d948da85e8 +[22]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/analyzer/video/quality_analyzing_video_encoder.h;l=54;drc=79020414fd5c71f9ec1f25445ea5f1c8001e1a49 +[23]: https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/test/pc/e2e/analyzer/video/quality_analyzing_video_decoder.h;l=50;drc=79020414fd5c71f9ec1f25445ea5f1c8001e1a49 +[24]: /test/network/g3doc/index.md |