Clarification needed for handling raw AAC bitstreams without description #832
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ChunMinChang
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Hmm, Chromium doesn't intentionally generate an audio specific config AFAIK. FFmpeg may be doing something under the hood though -- I doubt this works if we end up having to use a platform decoder. I don't know enough about AAC to say if there are forms where AAC can be decoded w/o the ASC. |
Very often you can make a good guess if you have the channel count / sample rate, and get something to decode fine by generating extradata. For example, here's some code that does it: https://searchfox.org/mozilla-central/source/dom/media/platforms/agnostic/bytestreams/Adts.cpp#273-287. Related: #826 (comment) |
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Due to the ongoing discussion in issue 832 [1], which has not yet reached a consensus among all parties, the AAC-without-description WPT introduced in the previous patch should be relocated to the *mozilla* folder under WPT. This ensures that the test remains specific to Mozilla and avoids unintentionally causing failures in other browers' test suites. [1] w3c/webcodecs#832 Differential Revision: https://phabricator.services.mozilla.com/D222712 bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1917721 gecko-commit: c81481c06eac3165b72e7bb2c3040a48b3994a0a gecko-reviewers: media-playback-reviewers, padenot
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…edia-playback-reviewers,padenot Due to the ongoing discussion in issue 832 [1], which has not yet reached a consensus among all parties, the AAC-without-description WPT introduced in the previous patch should be relocated to the *mozilla* folder under WPT. This ensures that the test remains specific to Mozilla and avoids unintentionally causing failures in other browers' test suites. [1] w3c/webcodecs#832 Differential Revision: https://phabricator.services.mozilla.com/D222712
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Due to the ongoing discussion in issue 832 [1], which has not yet reached a consensus among all parties, the AAC-without-description WPT introduced in the previous patch should be relocated to the *mozilla* folder under WPT. This ensures that the test remains specific to Mozilla and avoids unintentionally causing failures in other browers' test suites. [1] w3c/webcodecs#832 Differential Revision: https://phabricator.services.mozilla.com/D222712 bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1917721 gecko-commit: c81481c06eac3165b72e7bb2c3040a48b3994a0a gecko-reviewers: media-playback-reviewers, padenot
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…edia-playback-reviewers,padenot Due to the ongoing discussion in issue 832 [1], which has not yet reached a consensus among all parties, the AAC-without-description WPT introduced in the previous patch should be relocated to the *mozilla* folder under WPT. This ensures that the test remains specific to Mozilla and avoids unintentionally causing failures in other browers' test suites. [1] w3c/webcodecs#832 Differential Revision: https://phabricator.services.mozilla.com/D222712 UltraBlame original commit: c81481c06eac3165b72e7bb2c3040a48b3994a0a
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…edia-playback-reviewers,padenot Due to the ongoing discussion in issue 832 [1], which has not yet reached a consensus among all parties, the AAC-without-description WPT introduced in the previous patch should be relocated to the *mozilla* folder under WPT. This ensures that the test remains specific to Mozilla and avoids unintentionally causing failures in other browers' test suites. [1] w3c/webcodecs#832 Differential Revision: https://phabricator.services.mozilla.com/D222712 UltraBlame original commit: c81481c06eac3165b72e7bb2c3040a48b3994a0a
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…edia-playback-reviewers,padenot Due to the ongoing discussion in issue 832 [1], which has not yet reached a consensus among all parties, the AAC-without-description WPT introduced in the previous patch should be relocated to the *mozilla* folder under WPT. This ensures that the test remains specific to Mozilla and avoids unintentionally causing failures in other browers' test suites. [1] w3c/webcodecs#832 Differential Revision: https://phabricator.services.mozilla.com/D222712
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According to the AAC registration in WebCodecs, when the description is not present in AudioDecoderConfig, the bitstream is assumed to be in ADTS format. Otherwise, it's assumed to be in AAC. However, there's a case (https://webvideo-js.pages.dev/) where raw AAC data is provided to the audio decoder without supplying description data in configure beforehand (#826 seems a similar issue for opus).
Currently, Chrome can decode this raw AAC data, and Firefox has patches to support this behavior as well (by generating a AudioSpecificConfig).
This issue can be easily reproduced by adding a test case in audioDecoder-codec-specific.https.any.js WPT that replicates the properties of
MP4_AAC_DATAbut omits the description. I would like to ask if this behavior should be officially mentioned or detailed in the WebCodecs spec. If this use case is something that should be supported, it might be worthwhile to include a corresponding WPT for this scenario.The text was updated successfully, but these errors were encountered: