[FFmpeg-devel] H.264 + PAFF: BBC HD recording shows extreme interlacing artefacts

Reinhard Nissl rnissl
Mon Oct 29 00:23:47 CET 2007


M?ns Rullg?rd schrieb:

>>>>>> no, there is no problem with decoding, the problem is in the yv12->rgb
>>>>>> convertion, the fields have to be converted seperately not like a frame
>>> Is this a general rule, 
>> yes
>>> i. e. should this also be the case for MPEG2 frames when flag
>>> "interlaced_frame" is set?
>> yes in theory, in practice IIRC these flags are often set incorrectly by
>> the encoder
> The progressive_sequence flag in the MPEG2 sequence extension header
> is often misleadingly set to 0 due to soft telecine being used.  I say
> misleadingly, not incorrectly, since the spec allows any picture
> structure when this flag is 0.
> The flags in the picture header and picture coding extension are
> generally more reliable.

Hmm, I've read the relevant part of the MPEG2 spec again and come to
this conclusion:

a) there can be field pictures
b) there can be progressive frame pictures
c) there can be interlaced frame pictures

a) requires to do the colorspace conversion per field while for b) and
c) the colorspace conversion needs to be done per frame. Is this correct?

Is it correct that ffmpeg combines two field pictures into a frame picture?

In the case this is correct, how can I see, when to use the colorspace
conversion for a) or c) as interlaced_frame seems to be set in both cases?

In H.264 it seems that only a) and b) is possible. Is this correct?

Thanks for your assistance.

Dipl.-Inform. (FH) Reinhard Nissl
mailto:rnissl at gmx.de

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