[Ffmpeg-devel] MPEG 2 Quality Issues

[herve.flores]

Le 30 nov. 06 ? 11:40, Michael Niedermayer a ?crit :

> Hi
>
> On Wed, Nov 29, 2006 at 07:21:17PM -0600, Brian Brice wrote:
>> Hello.
>>
>> A while back I had emailed about bitrate issues regarding MPEG 2
>> encoding, and now I'm back for quality issues!  I have a DV clip
>> that contains some fast motion and I'm getting some horrible blocking
>> when trying to encode to MPEG 2.  I am trying to find the right  
>> options
>> to pass to ffmpeg that make a huge different in the quality of the
>> encoding.  I've used TMPGEnc and it produced *great* results, and  
>> I wish
>> I could get ffmpeg up to the same standard.  At this point I'm just
>> passing numbers without knowing what they do.
>>
>> I have tried setting lmin to 0 and lmax to 1*QP2LAMBDA.  This video
>> smooth like I would expect, but the bitrate ended up averaging around
>> 13.7 Mbps even though I tried to aim for CBR 7 Mbps.
>>
>> Here's a sample screenshot of how TMPGEnc looks to ffmpeg:
>> TMPGEnc: http://heapify.org/etc/ffm/tmpgenc.png
>> ffmpeg:  http://heapify.org/etc/ffm/ffmpeg.png
>> Major blocky-ness with ffmpeg :-(
>>
>> Here is the original clip:
>> http://heapify.org/etc/ffm/TestforMPG-Short.avi
>>
>> Encoded with ffmpeg without lmin/lmax settings:
>> http://heapify.org/etc/ffm/YuckNolminlmax.mpg
>>
>> Encoded with TMPGEnc, looks *great* as I want ffmpeg's to :-(
>> http://heapify.org/etc/ffm/TMPGEnc.mpg
>>
>> Here is how I used ffmpeg:
>> ffmpeg -i TestforMPG-Short.avi -y -f vob -vcodec mpeg2video - 
>> acodec mp2
>> -ab 384k -ar 48000 -ac 2 -aspect 4:3 -b 7000k -minrate 7000k -maxrate
>> 7000k -bufsize 1835008 -g 12 -bf 2 -flags ildct+trell -mbd 2
>> LooksGoodBadBitrate.mpg
>
> one thing missing here is -flags ilme
>
> [...]
> -- 
> Michael

...and "-top 0" (or "-top -1", it'll be the same here)

bye

Herv?