[FFmpeg-devel] [PATCH] libavformat/aac: Parse ID3 tags between ADTS frames.

[Richard Shaffer]

I did send the sample file and a unit test for this. If there are no
issues or other comments, would you guys be willing to merge it?

-Richard

On Fri, Feb 2, 2018 at 11:15 AM, Richard Shaffer <rshaffer at tunein.com> wrote:
> On Fri, Feb 2, 2018 at 5:52 AM, James Almer <jamrial at gmail.com> wrote:
>> On 2/1/2018 11:37 PM, rshaffer at tunein.com wrote:
>>> From: Richard Shaffer <rshaffer at tunein.com>
>>>
>>> While rare, ID3 tags may be inserted between ADTS frames. This change enables
>>> parsing them and setting the appropriate metadata updated event flag.
>>> ---
>>> I have encountered a streaming provider that I must support which does this.
>>> There are indications that it isn't totally off the wall, and that it does
>>> happen in the wild:
>>> * https://www.w3.org/TR/mse-byte-stream-format-mpeg-audio/
>>>   (See specifically sections 3 and 4.)
>>> * https://github.com/video-dev/hls.js/issues/508
>>>
>>> That being said, the providers that do this are in the minority. It seems most
>>> streaming providers will do one of the following:
>>>  1. If using .aac segments inside of HLS, use the #EXTINF for text metadata and
>>>     use an ID3 tag at the head of the segment for things like timing metadata.
>>>  2. If streaming raw AAC over HTTP, use Icy metadata.
>>>
>>> Aside from comments on the code, I'd be interested in any opinion about whether
>>> this is something that should or should not be supported in libavformat.
>>>
>>> Thanks,
>>>
>>> -Richard
>>
>> Can you provide a sample and add a fate test for this? To avoid
>> regressions in the future. This demuxer still needs some work.
>>
>> Use the new probetags() function you added in your other id3v2 test if
>> the tags between samples in the file are the only ones, or if they
>> differ in some way from the ones at the beginning of the file, so
>> ffprobe will report them instead.
>> Alternatively, see fate-adts-demux in tests/fate/demux.mak
>
> Oh, somebody did merge that test. How cool.
>
> I don't think we can test this with ffprobe, though. It will just read
> tags at the head of the file and not in the middle.
>
> I have at least one sample that's ok for me to share. I'll work on a
> separate patch to add a fate test.
>
> -Richard
>
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