Xvid decoder problem?

[sub]

I do understand your point of view also. Let me know if you manage to xvid working the way you want.

[nv40]

okay...yoda, you may have solved half of my problem. Your saying that by not inluding the 'vtag' option, it will create a regular divx file of the same quality, but roughly 15 percent larger? That is totally acceptable to me. My second question is about the 'qscale' tag. By adding this tag I can adjust the quality? What is the default value, since I want something a little higher?


edit: and as a side note. I have found the 'VLC media player' will handle just about any file, it's got to be the swiss army knife of media players. It's the only player I have that will play the xvid files with the wrong fourcc made by ffmpeg, and it also plays nero recode files, which are a propietary mp4 format that I didn't think any other player could handle.....there's no free codec for it!! oh...and the player is free!

[LilY0da]

selecting -vcodec mpeg4 will create a MP4 video. If you're using FFmpeg that comes with GBPVR, adding -vtag DIVX will flag it as a DivX video, adding -vtag XVID will flag it as a XviD.
In both cases, and assuming you have the software to play both DivX and XviD files installed on your PC, both should play without a problem, since in both cases, the FourCC is correct in the resulting files.

-qscale 4 seems to be a high quality vid. 384Mb for a 30 min video in 352x480 res, and I don't see any visible difference between this and a no compression XviD/DivX
I'd suggest you try out values between -qscale 4 and -qscale 10 and adjust for yourself

At equal quality, the -vcodec mpeg4 files are about 25~30% bigger than the -vcodec xvid ones, but they don't require you to reset the FourCC to correct the FFmpeg bug in -vcodec xvid mode. Also, it seems that mp4 encoding is slower than using the xvid mode in FFmpeg. Your choice. You have to decide if you want unattended transcoding with the mpeg4 mode, or smaller files and faster transcoding and the hassle of having to reset the FourCC with the xvid mode.

There's a couple more flags I used that seem to improve the transcoding quality, but since I'm at work, I won't be able to finish my testing until tonight or tomorrow. I'll post 2 updated lines to put in config.xml for both scenarios once I'm done.

If I manage to make a batch or .exe file to reset the FourCC in the files, I'll post it as well. But since I haven't found a free PHP compiler that seems easy to use, I'm going to have to learn another language, probably C to write a simple exe, or figure out a way to do this in a .bat
So if anyone wants to tackle that task, speak up...

[nv40]

Man..thanks....great info....please let me know about your results. I am basically looking for the quality of the original mpeg2, but at a smaller size. I know there is a limit to this....but I am willing to have bigger files than xvid in exchange for better quality.

[LilY0da]

Best results I have so far are below. Add to the config.xml and try out and optimize

Code:

<Conversion name="DivX Yoda" cmd="-y -i {SOURCE_FILE} -acodec mp3 -ab 128 -ac 2 -vcodec mpeg4 -vtag DIVX -aic -aiv -umv -ssm -hq -me full -nr -qns -deinterlace -trell -qscale 5 -aspect 4:3 {DEST_FILE}" targetExtension=".avi" />
    <Conversion name="XviD Yoda" cmd="-y -i {SOURCE_FILE} -acodec mp3 -ab 128 -ac 2 -vcodec xvid -vtag XVID -aic -aiv -umv -ssm -hq -me full -nr -qns -deinterlace -trell -qscale 5 -aspect 4:3 {DEST_FILE}" targetExtension=".avi" />

Also, even if my version has the -vtag option borked, I added it in there, for whoever has the normal GBPVR one. It will work in the case of DivX files, and not in the case of XviDs, forcing you to change the FourCC manually

If you want better quality, change to -qscale 4 or even -qscale 3, but watch out, the files seem to grow exponentially

[sub]

Since its not explicitly specified, what does it do with the bitrate? Do some some of the other arguments like -qscale imply a bitrate, maybe based on the original bitrate?

[nv40]

Best results I have so far are below. Add to the config.xml and try out and optimize

Code:

<Conversion name="DivX Yoda" cmd="-y -i {SOURCE_FILE} -acodec mp3 -ab 128 -ac 2 -vcodec mpeg4 -vtag DIVX -aic -aiv -umv -ssm -hq -me full -nr -qns -deinterlace -trell -qscale 5 -aspect 4:3 {DEST_FILE}" targetExtension=".avi" />
    <Conversion name="XviD Yoda" cmd="-y -i {SOURCE_FILE} -acodec mp3 -ab 128 -ac 2 -vcodec xvid -vtag XVID -aic -aiv -umv -ssm -hq -me full -nr -qns -deinterlace -trell -qscale 5 -aspect 4:3 {DEST_FILE}" targetExtension=".avi" />

Also, even if my version has the -vtag option borked, I added it in there, for whoever has the normal GBPVR one. It will work in the case of DivX files, and not in the case of XviDs, forcing you to change the FourCC manually

If you want better quality, change to -qscale 4 or even -qscale 3, but watch out, the files seem to grow exponentially

Thanks...i copied your 'divx' one over to my config file. I switched the qscale from 5 to 4. This should be a quality improvement over the original 'xvid' profile that came with gbpvr, correct? xvid took 30 minutes shows from 900 mb, down to about 300 mb.....what do you think this divx at qscale 4 would be? qscale 3? lower is higher quality, right?

[LilY0da]

Since its not explicitly specified, what does it do with the bitrate? Do some some of the other arguments like -qscale imply a bitrate, maybe based on the original bitrate?

-qscale sets the quantizer scale, which is equivalent to a percentage of error between the original and the encoded stream (if I understand it correctly, which isn't a given)
The bitrate will be variable, and will be what's needed to maintain that specified quality level. Quantizer values range between 2 and 31. The higher the quantizer, the more the compressor will ignore loss of data during the compression.

When you encode with a fixed bitrate (with the -b option) you can see the quantizer value used in real time.

To give you an idea of what is the resulting bitrate, during my tests, a -qscale 4 and XviD encoding takes an average of 1000Kbps for a 352x480 video, and about 1600Kbps for a 720x480.

I set the options up in config.xml tonight, hopefully I'll see the results tomorrow morning on some other recordings than the ones I used to test..

[LilY0da]

Thanks...i copied your 'divx' one over to my config file. I switched the qscale from 5 to 4. This should be a quality improvement over the original 'xvid' profile that came with gbpvr, correct? xvid took 30 minutes shows from 900 mb, down to about 300 mb.....what do you think this divx at qscale 4 would be? qscale 3? lower is higher quality, right?

the lower the quantizer (-qscale) the better the quality and the bigger the video
I have no idea what will be the resulting file size. Since it depends on the contents of the video, the video resolution, etc, you'll have to tell us

From what I saw, there is no visible difference between a quantizer of 2 (best quality possible, huge files) and 4. But then again my eyes aren't what they used to be, so let me know.
I'm far from being an expert in this, I just played around with the values for 2 days while I was pretending to work.

[nv40]

well....i copied your text for 'divx' word for word (i switched the qscale to 4), but nothing happened overnight. I deleted the default xvid profile in the config file, and pasted yours in it's place, was that correct?