[FFmpeg-devel] [PATCH] avformat/mpegenc - reject unsupported audio streams

[Gyan]

On 17-07-2019 02:23 PM, Carl Eugen Hoyos wrote:
>
>
>> Am 08.07.2019 um 14:05 schrieb Gyan <ffmpeg at gyani.pro>:
>>
>>
>>
>>> On 25-04-2019 01:48 PM, Gyan wrote:
>>>
>>>
>>>> On 25-04-2019 01:23 PM, Ali KIZIL wrote:
>>>>
>>>> There are also Dolby Codecs (ac3 & eac3). Will it also throw error for
>>>> these codecs ?
>>> AC3   is      supported before and after this patch.
>>> EAC3 is unsupported before and after this patch.
>>>
>>> But it's sent to the same decoder, so support could be added. I'll check.
>> Attached patch allows muxing EAC3 in MPEG-PS.  Stock ffmpeg can demux and decode such streams fine.
> Which descriptor is used for eac3?
> Please do not commit just because decoding works with FFmpeg, at least try to find some specification.

The PS muxer appears to use System A and this is what the ATSC A/52 
(2012) standard says,

"For System A, this section extends the use ofthe AC-3 Registration 
Descriptor defined in Section A3 in combination with the E-AC-3 
stream_type value defined below."

and

"E-AC-3 bit streams shall be identified with a stream_typevalue of 0x87 
when transmitted as PES streams conforming to ATSC-published standards."

Note that the stream_type value of AC-3 is 0x81 yet our id sequence 
starts from 0x80.  This patch uses the same descriptor series as AC-3, 
however if I switch to 0x87, only one such stream may be muxed as 0x88 
was assigned (by you) to DTS. Also, our demuxer sets the codec_id to DTS 
for 0x88 to 0x8f.

Both stock ffmpeg and VlC 4.0 nightly play files using the current 
patch. Mediainfo also identifies the codec correctly.

Comments?

Gyan