Avi support

[Bart]

Jorm, about the problems with VLC - a response from the devel list:

...
>> It's been a while since I used VLC, recently I noticed that transcoding
>> a file towards a MPEG2-PS or TS, the 'duration' of the created file is
>> corrupted/incorrect (transcode and open with VLC and see duration of
>> file). If I mux (mp2v and mp2a) it on MP4 it seems to be fine.
>>
>> Is this a known limitation is there a fix on this, searching through the
>> archives didn't answer the question?

ANWER from developers:

"AFAIK, this is related to the "fps" field being set to 0 by VLC's ps
muxer. So, yes, it is a flow in VLC... not sure it is easy to fix..."

[jorm]

Have you noticed that the there are a lot of artifacts with mencoder. Maybe it is just my source. Wonder if there is a argument to increase the bit rate.

[colin]

The problem will be your src file. Depending on how heavily it was filtered/compressed into the avi will greatly affect its conversion to mpeg.

mencoder has a lot of options to tweak. probably best looking at http://www.mplayerhq.hu/homepage/design7/news.html as they should have links to manpages etc.

You may consider QuEnc which takes an avisynth script which allows you to do some filtering to help improve the image quality,

check out sites like doom9.org or kvcd.net for more info on video processing,

cheers,
Colin.

[Bart]

Quote[/b] (jorm @ Feb. 04 2005,01:28)]Have you noticed that the there are a lot of artifacts with mencoder. Maybe it is just my source. Wonder if there is a argument to increase the bit rate.

http://www.mplayerhq.hu/DOCS....20ONLY)

vbitrate=<value>
Specify bitrate (pass 1/2) (default: 800).
WARNING: 1kBit = 1000 Bits
4-16000
(in kbit)
16001-24000000
(in bit)

You could try to increase it and try the same scene again.

I see two options: first see reaction Colin - if input is lousy...

Second: are the artifacts possibly (only) in real fast scenes (so lots of camera movement and/or changes of images, explosions etc ?)

In the that case, the mpeg decoder might miss sufficiant information to be able to build the frames: complex images and fast changes require more data wich might lag due to the available bitrate/compression. So in that case, indeed the vbitrate might make a difference. I have only tested with some xvids trailers, but will try some fast scenes tonight

The documentation describes that the default vbitrate = 800K that is far too little for a decent MPEG2 (is rather MPEG1). For a descent MPEG2 it's common to have from 3 upto 9 Mbit/s (or higher up depending on input quality). So raise the vbitrate a little.

Further on, I read some stuff on the keyintervalls that can be set:

" keyint=<0-300>
maximum interval between keyframes in frames (de- fault: 250 or one keyframe every ten seconds in a 25fps movie). Keyframes are needed for seeking as seeking is only possible to a keyframe, but keyframes need more space than other frames, so larger numbers here mean slightly smaller files but less precise seeking. 0 is equivalent to 1, which makes every frame a keyframe. Values >300 are not recommended as the quality might be bad depending upon decoder, encoder and luck. For a strict MPEG-1/2/4 compliance this would have to be <=132."

There's no description on the default, but I had problems with seeking through a transcoded asset, so this could be the key

regards,
Bart

[sash]

@emb

the chances are, the reason mp2 doesnot work in VLC, is because there is no option mp2 in vlc 7.2
in vlc for audio. the closes would be mpga


for transcoding these are your options:
Video
mpeg1= mp1v ; mpeg2 = mp2v; mpeg4= mp4v; ...ect

audio:
mpeg1= mpga; mp3=mp3; mpeg4= mp4a; ....etc

but all these setting can be found in the commanline generator- under streaming

[colin]

First thing before messing with mencoder options is check the quality of your src file. If the artifacts, mosquitos, etc are in the src, then you're going to need to do some filtering on it but its going to be hard to produce a good quality mpeg if the src is not great.

If the src is good, try the suggestions by Bart, and I think mencoder has some filters which you can take advantage of.

the keyint that Bart mentioned, I thought was the I frame of which you should have 1 per GOP. The rest of the GOP is composed of B-frames and P-frames which take up less space then the I-frame. To comform to standards then GOP's should be of certain lengths, though the longer they are the more compression you can achieve. Of course quality is affected, so then other measures need to be taken to try and assist there.

anyway, have fun,

Cheers,
Colin.