[FFmpeg-devel] MP3 streaming/seeking broken in new Chrome release using newer ffmpeg

[Ronald S. Bultje]

Hi Andrew,

On Thu, Sep 10, 2015 at 8:37 AM, Clément Bœsch <u at pkh.me> wrote:

> On Thu, Sep 10, 2015 at 08:35:21PM +1000, Andrew Armstrong wrote:
> > Hello,
> >
> > A recent Chrome update today has caused seeking in audio files streamed
> on
> > the web (eg, via SoundCloud and others) to no longer work. Instead, the
> > file is slowly buffered until the required position in the data stream is
> > reached.
> >
> > I added some notes about this problem at the Chrome bug report list at
> > https://code.google.com/p/chromium/issues/detail?id=530043
> >
> > I'm not sure how to directly test this in the ffmpeg toolset, perhaps it
> > has been corrected in a recent commit? Please see below for my analysis.
> >
> >
> > *ANALYSIS*
> > ffmpeg has been updated in the new Chrome release. Various mp3 seeking
> > commits were included that made large changes, breaking this feature.
> Other
> > commits have since been added that have not been merged in, I do not know
> > if these fix the issue - potentially.
> >
> > I noticed a new seek "mode" was added to ffmpeg for mp3's that causes
> > seeking to either by disabled or use the "slow but accurate" mode of
> > reading data until the byte position is available, instead of causing a
> > seek like before.
> >
> > This commit, which was not part of the merge, is also of interest
> >
> https://github.com/FFmpeg/FFmpeg/commit/c43bd08f8b043df7e18110e5344283c37b8380c1
> >
> > *DETAILS*
> > I noticed that ffmpeg was updated, and ffmpeg had a lot of changes
> > regarding mp3 seeking, and more changes after the commit that Chrome
> merged.
> >
> > 1. Chrome stable release diff:
> >
> https://chromium.googlesource.com/chromium/src/+log/44.0.2403.157..45.0.2454.85?pretty=fuller&n=10000
> >
> > 2.These are the ffmpeg DEPS submodule versions
> > 44x ffmpeg deps: ffmpeg cc2ec2825b0cc25cf27c5843847e7028c1cdb075
> > 45x ffmpeg deps: ffmpeg 833732528c1873f37b490b289eeaded2ae86349c
> >
> > 3. Diff of ffmpeg from the previous stable release to this one:
> >
> https://chromium.googlesource.com/chromium/third_party/ffmpeg.git/+log/cc2ec2825b0cc25cf27c5843847e7028c1cdb075..833732528c1873f37b490b289eeaded2ae86349c
> >
> > 4. Commits affecting mp3 seeking in this diff:
> > avformat/mp3: large id3 tags break concatenated file detection
> >
> https://chromium.googlesource.com/chromium/third_party/ffmpeg.git/+/537ab680534e53bd298ba3f62d4aabb56afcd403
> >
> > avformat/mp3dec: fix gapless audio when seeking in CBR mode
> >
> https://chromium.googlesource.com/chromium/third_party/ffmpeg.git/+/92eef26e67ea8d2265854594344f8db17b9ce299
> >
> > avformat/mp3dec: Allow forcing the use of the xing TOC for CBR files
> >
> https://chromium.googlesource.com/chromium/third_party/ffmpeg.git/+/a742a0536dbb8b5a280b21ffd76c8b4acdbd20a6
> >
> > avformat/mp3dec: offset seek index to end of id3v2 tag
> >
> https://chromium.googlesource.com/chromium/third_party/ffmpeg.git/+/8b76c0eb561b0313e2a27950fe9d2bc5e4780dd8
> >
> > avformat/mp3: skip junk at the beginning of mp3 files
> >
> https://chromium.googlesource.com/chromium/third_party/ffmpeg.git/+/2b3e9bbfb529e6bde238aeb511b55ebe461664c8
> >
> > avformat/mp3dec: allow enabling generic seek mode
> >
> https://chromium.googlesource.com/chromium/third_party/ffmpeg.git/+/c3a73666ad1eee93e49f25efae30fda5556c228e
> >
> > 5. I notice that further commits, that were not merged, have been made to
> > ffmpeg seeking at
> >
> https://github.com/FFmpeg/FFmpeg/commit/c43bd08f8b043df7e18110e5344283c37b8380c1
> >
>
> So which commit is responsible of the regression?


Also, what code does Chrome invoke to seek? I assume it calls
av_seek_frame() - with which arguments?

Ronald