[FFmpeg-devel] [PATCH] ADTS Muxer: Refuse to write out illegal ADTS files

[Alex Converse]

On Thu, Feb 12, 2009 at 6:58 AM, Robert Swain <robert.swain at gmail.com> wrote:
> 2009/2/12 Alex Converse <alex.converse at gmail.com>:
>> Right now we are part of the problem.
>
> :)
>
>> diff --git a/libavformat/adtsenc.c b/libavformat/adtsenc.c
>> index 5c65d36..9566872 100644
>> --- a/libavformat/adtsenc.c
>> +++ b/libavformat/adtsenc.c
>
>> @@ -41,6 +41,19 @@ static int decode_extradata(ADTSContext *adts, uint8_t *buf, int size)
>>      adts->sample_rate_index = get_bits(&gb, 4);
>>      adts->channel_conf = get_bits(&gb, 4);
>>
>> +    if (adts->objecttype > 3) {
>> +        av_log(s, AV_LOG_ERROR, "MPEG-4 AOT %d is not allowed in ADTS\n", adts->objecttype);
>> +        return -1;
>> +    }
>
> The error message is correct for "MPEG identifier" == 0 but not for ==
> 1. If ID == 1, the object types pertain to MPEG-2 AAC profiles as per
> "Table 1.A.11 ? MPEG-2 Audio profiles and MPEG-4 Audio object types".
> Also note that object type == 3 is reserved for ID == 1.
>

We should be setting ID to 0 unless we can prove (or it's otherwise
signaled to us) that no MPEG-4 only features (not just LTP, the rare
960 frame length, PNS) are being used in the stream.

The first two are easy to check for. The third requires parsing every
frame. Thus for now we should be setting ID=0. If there is a command
line way to pass options to a muxer, forcing ID=1 would be an
interesting option.

Regards,
Alex