[Ffmpeg-devel] [PATCH] correctly set profile/level for mpeg2 hd

[Baptiste Coudurier]

Hi

Michael Niedermayer wrote:
>> [...]
>> Index: libavcodec/mpeg12.c
>> ===================================================================
>> --- libavcodec/mpeg12.c	(revision 7707)
>> +++ libavcodec/mpeg12.c	(working copy)
>> @@ -234,11 +234,19 @@
>>          }
>>      }
>>  
>> -    if(avctx->profile == FF_PROFILE_UNKNOWN)
>> +    if(avctx->profile == FF_PROFILE_UNKNOWN) {
>> +        if (avctx->width > 720 || avctx->height > 576)
>> +            avctx->profile = 1; /* High Profile */
>> +        else
>>          avctx->profile = s->chroma_format == CHROMA_420 ? 4 : 0;
> 
> this is incorrect, such resolutions do not need high profile

This is correct, they do not need it, except when 422 chroma,
and we could use 422P profile when height is 608.

>> +    }
>>  
>> -    if(avctx->level == FF_LEVEL_UNKNOWN)
>> +    if(avctx->level == FF_LEVEL_UNKNOWN) {
>> +        if (avctx->width > 720 || avctx->height > 576)
>> +            avctx->level = 4; /* High Level */
> 
> High 1440 profile seems sufficient here
> anyway either set these values correctly or dont set them

What about 4:2:2 chroma format ? Only High profile and 4:2:2 support it
at such resolutions.
Those profile/level I set with the patch are correct,
they englobes all combinations with the smallest code.

If you prefer, I'll use the least requiring profile for all
chroma/resolution combinations.

> 
> [...]
>> -                put_bits(&s->pb, 1, s->chroma_format == CHROMA_422); //escx
>> +                put_bits(&s->pb, 1, s->avctx->profile == 0); //escx 1 for 4:2:2 profile */
> 
> my mpeg2 draft says non 0 is reserved, so this will need some
> explanations
> 

Quote from ISO 13818-2 2000:
"Table 8-4 describes profiles and levels when the escape bit equals 1.
For these profiles and levels there is no implied hierarchy from the
assignment of profile_and_level_indication and profiles and levels
are not necessarily subsets of
others."

4:2:2 profile always use escape bit to one. Multi view profile uses it
too, but I don't know if encoder supports it.

10000101 4:2:2 profile @ Main level
10000010 4:2:2 profile @ High level

-- 
Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
SMARTJOG S.A.                                    http://www.smartjog.com
Key fingerprint                 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA
Phone: +33 1 49966312