Re: [FFmpeg-devel] [PATCH] avcodec/aac_parser: fix aac profile probing

[Nicolas Gaullier <nicolas.gaullier@cji.paris>]

On 6/26/25 19:30, Baptiste Coudurier wrote:
> Hi Nicolas
>> On Jun 26, 2025, at 4:06 AM, Nicolas Gaullier <nicolas.gaullier@cji.paris> wrote:
>>
>> On 6/17/25 13:41, Nicolas Gaullier wrote:
>>> Reverts 64bb91fd3b5a00a8849531c7e8dd207f2a626096 except the
>>> key_frame setting for aac.
>>> See also 696ea1c2236842572df88d573e24a39be3f19c98.
>>> Don't force the profile as it may override the correct value
>>> set by the decoder (HE/HEv2).
>>>
>>> Fixes #11600
>>>
>>> Signed-off-by: Nicolas Gaullier <nicolas.gaullier@cji.paris>
>>> ---
>>>   libavcodec/aac_ac3_parser.c | 8 +++-----
>>>   1 file changed, 3 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/libavcodec/aac_ac3_parser.c b/libavcodec/aac_ac3_parser.c
>>> index e10ce13a3b..1dcc2e735f 100644
>>> --- a/libavcodec/aac_ac3_parser.c
>>> +++ b/libavcodec/aac_ac3_parser.c
>>> @@ -147,15 +147,13 @@ get_next:
>>>           } else {
>>>   #if CONFIG_AAC_PARSER
>>>               AACADTSHeaderInfo hdr;
>>> -            GetBitContext gb;
>>>   -            init_get_bits8(&gb, buf, buf_size);
>>>               if (buf_size < AV_AAC_ADTS_HEADER_SIZE ||
>>> -                ff_adts_header_parse(&gb, &hdr) < 0)
>>> +                ff_adts_header_parse_buf(buf, &hdr) < 0)
>>>                   return i;
>>>   -            avctx->profile = hdr.object_type - 1;
>>> -            s1->key_frame = (avctx->profile == AV_PROFILE_AAC_USAC) ? get_bits1(&gb) : 1;
>>> +            /* ADTS does not support USAC */
>>> +            s1->key_frame = 1;
>>>               bit_rate = hdr.bit_rate;
>>>   #endif
>>>           }
>> Ping ?
>>
>> https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=14810
>>
> How hard is it to detect HEAACv2 in the parser ? Maybe only set it if profile is unknown?
> It’s usually nice when parser can set profile.
>
> —
> Baptiste

Yes, you're right, I had the same feeling when reverting this...

It does not seem so straightforward, because aac seems very modular 
while not using signaling, but it must be doable someway.

I will dig into this and see if I can come up with something satisfactory...

I think it would be an additional patch, and this one should remain the 
basic revert which, mostly, simply removes dead code.

Maybe it would be desirable to follow this patch immediately with a new 
patch that could restore the "profile setting" thing correctly, but that 
would add some undetermined delay, so I would say it is best to apply 
this patch on its own.

Nicolas

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