making a good quality avi from ts, vob etc

[pooksahib]

Hi. It seems that, whenever someone uploads a “DVDrip”, the format is .avi which I presume is to have a smaller file size than the original .vob.


I downloaded the first series of one of my favourite TV shows and each episode (of very good picture quality) has these specs:


Format : AVI
Format/Info : Audio Video Interleave
File size : 236 MiB
Duration : 28mn 35s
Overall bit rate : 1 154 Kbps
Writing application : VirtualDubMod 1.5.10.2 (build 2540/release)
Writing library : VirtualDubMod build 2540/release


Video
ID : 0
Format : MPEG-4 Visual
Format profile : Advanced Simple@L5
Format settings, BVOP : 2
Format settings, QPel : No
Format settings, GMC : No warppoints
Format settings, Matrix : Default (H.263)
Muxing mode : Packed bitstream
Codec ID : XVID
Codec ID/Hint : XviD
Duration : 28mn 35s
Bit rate : 1 016 Kbps
Width : 608 pixels
Height : 336 pixels


I have the second series recorded on my PVR and have transferred the .ts files to my PC. Using xmediarecode, I converted them to .avi and these are the specs:


Format : AVI
Format/Info : Audio Video Interleave
File size : 335 MiB
Duration : 28mn 30s
Overall bit rate : 1 643 Kbps
Writing application : Lavf53.9.0


Video
ID : 0
Format : MPEG-4 Visual
Format profile : Advanced Simple@L5
Format settings, BVOP : No
Format settings, QPel : No
Format settings, GMC : No warppoints
Format settings, Matrix : Default (H.263)
Codec ID : XVID
Codec ID/Hint : XviD
Duration : 28mn 30s
Bit rate : 1 502 Kbps
Width : 720 pixels
Height : 576 pixels


As you can see, I specified a higher bit rate and so ended up with a larger file than the ones I downloaded. The downloaded files play equally well on my PC and TV (via a media player) but the file I created only looks decent on the PC. On the TV, it's quite 'blocky'.


So what's the secret of creating a good, reasonably sized .avi file from sources such as .ts and .vob?


Many thanks for any advice offered.

[jagabo]

Start with a DVD, not a broadcast source. And downsize your video. The bigger the frame the more bitrate it will require. Of course, what you'll be doing is trading away resolution to get less blocking.

Regarding computer vs TV viewing: the xvid decoder on your computer may be using a deblocking filter. Stand alone players usually don't have deblocking filters. For example, Xvid's decoding options:

[pooksahib]

Thanks jagabo. I don't normally concern myself with DVDs, it's just the odd TV program that I like to archive but in a reasonable file size. Good news though - using xmediarecode again, I manually specified a frame width of 624 and a bit rate of 1000. There was no sign of xvid decoding options in the style you posted but as you can see, I AM using xvid and there is a deblocking option. This must be a feature of xmediarecode as you can choose deblocking no matter which video codec is selected. Anyway, I chose medium deblocking and, with the other specs referred to above, ended up with a video that plays fine on both PC and TV.

Thanks again.

[jagabo]

The deblocking options you show are filters applied to the video by xmediarecode before encoding. You should use that if your source has a lot of blocking.

To get to the Xvid playback deblocking options go to Start -> All Programs -> Xvid -> Configure Decoder. That controls the deblocking while the video is being played. The media player must be using Xvid to decode the video, not some other MPEG 4 Part 2 decoder.

[pooksahib]

The world of video editing is very complex isn't it? I don't have Xvid installed as a Program (and don't want to if I don't need to - all vids play fine on my PC) so I can't configure it in the way you suggest. I've no idea which decoder my "WDTV Live Hub" uses. Maybe it was the smaller frame size that caused my previous experiment to have a satisfactory outcome. I'll maybe try a few different conversions to see what makes it better/worse when played to the TV.

Continued thanks to you.

[jagabo]

The xvid deblocking options have nothing to do with encoding. They are applied during playback, and only when Xvid is being used to decode the video. The WDTV live uses a hardware MPEG 4 Part 2 decoder chip. It doesn't have any deblocking features.

[pooksahib]

Sorted. I've done conversions using xmediarecode's "WDTV" preset and also a custom avi with mpeg4 as the codec. Set bit rate at 1200 and they're all fine. File size now one third of original. Great stuff, thank you.

[jagabo]

Why use bitrate based encoding? Every video is different and requires a different amount of bitrate. 1200 kbps will be too much for some videos, too little for others. Try constant quality encoding instead. That way every video is encode with the same quality. The encoder uses whatever bitrate is necessary to achieve that quality. And constant quality encoding is faster since it can be done in a single pass.

Use 2-pass bitrate based encoding when you need a file of a particular size. Like when you need to put a 90 minute movie on a 700 MB CD. You know what size video will turn out but you don't know what the quality will be.

Use single pass quality based encoding when you want to be assured of quality. You know what the quality will be, but you don't know the size.

I don't know what terms xmediarecode uses, but the Xvid codec calls quality based encoding Target Quantizer. If you have that as an option try using a Quantizer of 3. That's a good compromise of quality vs file size. A Quantizer of 2 will give slightly higher quality and larger files, a Quantizer of 4 will give lower quality and smaller files. You can use anywhere from 1 to 31. Experiment with a few short videos to see what's acceptable to you. Some programs have a "Quality" setting that ranges from 0 to 100. 0 is the lowest quality, 100 the highest.

[pooksahib]

Interesting and something to think about. In my case, I sometimes find myself with a file of very high quality and simply want a copy of it that doesn't take up as much space. So I use mediainfo to find out the bitrate of the original and then convert it with a specified bitrate of approx one third of that figure. If the resultant vid is poor, I re-do it with a bitrate of half the original.

Xmediarecode allows for Constant Bitrate, 2-pass Variable Bitrate and Constant Quantizer. I've only ever used the former so may try the Quantizer option next time.

All the best.