[FFmpeg-devel] [PATCH] ffmpeg: Carry streamid as metadata key 'id'

[James Almer]

On 4/15/2024 9:30 PM, Michael Niedermayer wrote:
> On Mon, Apr 15, 2024 at 10:35:44AM +0200, Tomas Härdin wrote:
>> lör 2024-04-13 klockan 01:25 +0200 skrev Michael Niedermayer:
>>> On Fri, Apr 12, 2024 at 11:40:47AM +0200, Tomas Härdin wrote:
>>>> This idea could be extended to other fields not presently
>>>> considered to
>>>> be metadata, that would be handy to treat as such.
>>>>
>>>> I use the key "id" because ffprobe outputs id= for streamid.
>>>> Another
>>>> option could be to collect these types of metadata that go into
>>>> AVStream fields under a namespace like FFMPEG: or AVSTREAM: or
>>>> something, then delete all of them using AV_DICT_IGNORE_SUFFIX near
>>>> the
>>>> end of of_open() since they're for internal ffmpeg use.
>>>>
>>>> The FATE change is just because av_dict() changes the order of
>>>> things
>>>> when elements are deleted.
>>>>
>>>> /Tomas
>>>
>>>>   fftools/ffmpeg_demux.c              |    5 +++
>>>>   fftools/ffmpeg_mux_init.c           |   56
>>>> ++++++++++++++++++++++++++----------
>>>>   tests/ref/fate/matroska-stereo_mode |    6 +--
>>>>   3 files changed, 49 insertions(+), 18 deletions(-)
>>>> cd526b2292b6d7e3fb5739a04cf17fbe5f207f16  0001-ffmpeg-Carry-
>>>> streamid-as-metadata-key-id.patch
>>>>  From 7799f1b2eb8ab02e58118565f3e889fbe0d568a7 Mon Sep 17 00:00:00
>>>> 2001
>>>> From: =?UTF-8?q?Tomas=20H=C3=A4rdin?= <git at haerdin.se>
>>>> Date: Fri, 12 Apr 2024 10:34:12 +0200
>>>> Subject: [PATCH] ffmpeg: Carry streamid as metadata key 'id'
>>>>
>>>> This allows using -map_metadata and -metadata to copy/set streamids
>>>> (PIDs).
>>>> ---
>>>>   fftools/ffmpeg_demux.c              |  5 +++
>>>>   fftools/ffmpeg_mux_init.c           | 56 +++++++++++++++++++++----
>>>> ----
>>>>   tests/ref/fate/matroska-stereo_mode |  6 ++--
>>>>   3 files changed, 49 insertions(+), 18 deletions(-)
>>>
>>> breaks:
>>>
>>> ./ffmpeg -i ~/videos/mm-short.mpg -vstats_file /tmp/vstats -bitexact
>>> -map 0:1 -map 0:1 -map 0:2 -threads 6 -vcodec libx264 -vcodec libx264
>>> -pass 1 -b:v:0 300k -b:v:1 900k -passlogfile:v:1 /tmp/video2 -
>>> passlogfile:v:0 /tmp/video1 -t 1 -y -ab 128k  /tmp/x.ts
>>>
>>> [mpegts @ 0x558d5e3b2140] Duplicate stream id 480
>>
>> It's hardly strange if you map the same stream to the output twice that
>> you get duplicate streamids
> 
> ok but asking for a stream to be mapped twice is a valid case.
> Ideally FFmpeg should not fail, it should resolve all parameters
> within what is valid.
> It could fail if the user explcicitly asks for invalid parameters ...

mpegts muxer could change the duplicate id for a free one. Afaik the 
field is documented as being modifiable by muxers. It could also do it 
internally.