[FFmpeg-devel] [PATCH 2/2] avformat: add mapping for AC-4 in MP4

[James Almer]

On 2/17/2019 6:14 PM, Paul B Mahol wrote:
> On 2/17/19, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>> 2019-02-17 21:50 GMT+01:00, Paul B Mahol <onemda at gmail.com>:
>>> On 2/17/19, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>>>> 2019-02-17 21:25 GMT+01:00, Paul B Mahol <onemda at gmail.com>:
>>>>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>>>>> ---
>>>>>  libavformat/isom.c | 1 +
>>>>>  1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/libavformat/isom.c b/libavformat/isom.c
>>>>> index 0a4d901be5..0052db539e 100644
>>>>> --- a/libavformat/isom.c
>>>>> +++ b/libavformat/isom.c
>>>>
>>>>> +    { AV_CODEC_ID_AC4,             MKTAG('a', 'c', '-', '4') },
>>>>> /* ETSI TS 103 190 */
>>>>
>>>> Are there no codec-specific atoms needed when remuxing ac-4?
>>>
>>> They are completely optional and not needed for decoding or remuxing.
>>
>> Thank you for the explanation!
>> Do we already have samples?
>>
> 
> http://testassets.dashif.org/#feature/details/586fb3879ae9045678eab593

There's a dac4 atom inside the Audio Sample Entry, much like AC-3 has a
dac3 and EAC-3 a dec3 atom.
Are you sure it's optional? Codec specific atoms inside the stream's
Video/Audio Sample Entry tend to be obligatory.