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When applying an MP4 edit list, preroll and skip samples from a keyframe to the start of an edit #1659

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sanmall opened this issue Jul 8, 2016 · 4 comments
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When applying an MP4 edit list, preroll and skip samples from a keyframe to the start of an edit #1659

sanmall opened this issue Jul 8, 2016 · 4 comments
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@andrewlewis
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enhancement low priority

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@sanmall
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sanmall commented Jul 8, 2016

video recorded from ios can not play in front of a few seconds, but the audio is ok.
@sanmall
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sanmall commented Jul 8, 2016

eg：http://biubiustorage.oss-cn-shenzhen.aliyuncs.com/a7/dc/a7dc023ba53fccb5ded0be16f936266cbca10ac15e202aaa8eee30b1b8e0d048.mp4

@ojw28 ojw28 added the bug label Jul 8, 2016
@andrewlewis
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This file contains an edit list that skips the first video frame, which is a keyframe. Due to a limitation in how we handle edit lists (see this comment) we don't send the frame to the decoder, which means samples are dropped up to the next key-frame. This is why video starts playing late.

I'll use this issue to track the enhancement of extracting and skipping samples from the latest keyframe at/before an edit up to the start of the edit. I think it's unlikely we will prioritize it in the near future, unless we find that this type of stream is common. Thanks!

@andrewlewis andrewlewis changed the title video recorded from ios can not play in front of a few seconds When applying an MP4 edit list, preroll and skip samples from a keyframe to the start of an edit Jul 18, 2016
@andrewlewis andrewlewis mentioned this issue Oct 20, 2016
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@ojw28 ojw28 mentioned this issue Jun 5, 2017
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@tonihei tonihei mentioned this issue Jul 5, 2018
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@andrewlewis andrewlewis mentioned this issue Dec 4, 2018
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@kim-vde kim-vde mentioned this issue Apr 14, 2021
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@greyson-signal
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Hi there, just wanted to say that we're hitting this issue at Signal. Videos recorded by iOS devices that are then sent and played back by ExoPlayer on an Android device will sometimes run into this. It doesn't seem to be all videos transcoded by iOS, but some.

@icbaker icbaker mentioned this issue Feb 22, 2023
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copybara-service bot pushed a commit to androidx/media that referenced this issue Sep 11, 2024
@rohitjoins @copybara-github
Fix preroll sample handling for non-keyframe media start positions
f133e8d 
When processing edit lists in MP4 files, the media start position may be a non-keyframe. To ensure proper playback, the decoder must preroll to the preceding keyframe, as these preroll samples are essential for decoding but are not rendered.

Issue: google/ExoPlayer#1659

#cherrypick

PiperOrigin-RevId: 673457615
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This issue has now been fixed.

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@andrewlewis @ojw28 @sanmall @rohitjoins @greyson-signal