[Ffmpeg-devel] MPEG 2 Quality Issues

[Víctor Paesa]

Hi,
>
> 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)
>

Is -top really needed here?

I tried SVN-r7186 with -top 0, with -top -1 and whitout -top,
and I got three binary identical results.

(I tried with a PAL DV on AVI file, I don't know if NTSC behaves
differently)

Regards,
V?ctor