Intermediate codec and xvid question, and xvid to wmv.

[^xRun^]

Hi.
I record many hours every week of high quality streamed video and audio from a subscription service with a TV channel here in Norway. I've been using computers for a while, but am not savvy when it comes to all the different tools out there.

I allways convert the .asf file to xvid, but do some audio and video filtering before I get to the final compression, so it would be preferrable to store the filtered file in a very high quality low compression codec.
What is a good codec with very high quality to use for this? If it's fast that's very good too.

I have been using high bitrate xvid as intermediate so far and it's been looking good, allthough the bitrate in the files never go much above 4000kbit even though I set the bitrate to 8000, just to get a high quality editable file to work with. Any solutions for that? Alternately, any good tool to convert .asf-files to avi in very high quality and preferrably in a quick fashion?

I have loads of storage space but not very much time, and I'd like not to waste space in the final file for archiving, so that'll be compressed in xvid at around 1024kbit and dual pass.

Also another question... do you know any transcoder that'll batch convert xvid AVI's with custom frame sizes and 2 passes for optimal quality? to wmv?
I've been looking into River Past Video Cleaner, but it doesnt do 2-pass, and I've had little luck finding a good tool to do this.

You'll find a jpg here with a side-by-side comparison of the videostream I'm recording, and the result I'm getting so far.

cs_side-by-side_compare.jpg

[jagabo]

I have been using high bitrate xvid as intermediate so far and it's been looking good, allthough the bitrate in the files never go much above 4000kbit even though I set the bitrate to 8000, just to get a high quality editable file to work with. Any solutions for that?

Forget bitrate. Set Xvid to single pass target quantizer (constant quality) mode. Disable B frames. Set the quantizer (1/quality) to the quality you want. At 2 you will hard pressed to see any differences even looking at enlarged still frames side by side. If you want even higher quality set the quantizer to 1 but the size will probably turn out larger than your source. If you want smaller files try 3 -- a good compromise between file size and quality. The higher you set the quantizer the lower the quality and file size you'll get. The quality presets won't make any difference in the quality in Target Quantizer mode. But the lower the settings the bigger the files will be.

You might consider using Divx instead of Xvid. At its fastest settings (otherwise similar to the Xvid settings above) it is more than twice as fast as Xvid. Files will be even larger though.

For intermediate codecs (where you want to store something with very high quality for a short period of time, and will make a final compression later) you want to use something lossless like HuffYUV or Cedocida. MJPEG is lossy but at it's highest quality settings is pretty transparent. These are all much faster than Xvid. But won't deliver small file sizes.

[^xRun^]

Ok, since storage is no problem, and I'll gladly store 2 or 3 MB/sec for the intermediary file, I'll try setting it to 1 then, just so that I don't get any noticable loss at all.
As you can see in the pic I posted above, I'm allready getting pretty good results, but I wanna improve even more and also speed up the process a little.
So question is which is faster, quantizer at 2 or 1? Cause I have a deadline for finished edited/filtered files in AVI and WMV by next midnight for the recording at any given morning, and the show is usually 2-3 hours long.
I also need some way to encode the files in dualpass to WMV in order to get most of the image quality in that format, even at 512kbit for streaming. Right now I'm doing single pass wmv encoding, and the quality is not quite there unless I go for larger files.

[jagabo]

So question is which is faster, quantizer at 2 or 1?

Quantizer 2 will be a tiny bit faster because it will spend less time writing to disk. But the difference will likely be insignificant.

I happened to run a few quick test the other day. I compressed a 90 second 23.976 fps 720x480 MPEG video with several different codecs:

https://forum.videohelp.com/topic353988.html#1869407

Notice that Divx compressed at over 12x realtime. So a 3 hour show would compress in less than 15 minutes.

[^xRun^]

That's very good, but I think I'll stay with one mpeg4 codec at a time, xvid's still faster than realtime so it's not all that bad. The challenge becomes to compress the edited and filtered intermediary to xvid avi and wmv in a 2-pass run for max quality and still be done by midnight.

Just ran a test with xvid compression of a 163second long test recording, Q2 gave a 64.8MB file in 237 seconds on this computer, and at Q1 it got a 198MB file in 283 seconds. It's not the fastest computer, but I think I'll go for Q1 and still be ok for time, allthough it's 1.74 times slower than realtime.
As I said, the thing that may take the most time is 2-pass encoding to xvid and to wmv in the evening.

Thanks for the help, I'm guessing at Q1 the xvid codec will throw as many bits at anything that moves as it possible can, so that'll be the high quality intermediary I was looking for.

[jagabo]

Just ran a test with xvid compression of a 163second long test recording, Q2 gave a 64.8MB file in 237 seconds on this computer, and at Q1 it got a 198MB file in 283 seconds. It's not the fastest computer, but I think I'll go for Q1 and still be ok for time, allthough it's 1.74 times slower than realtime.

Turn off B-frames (they are normally encoded at lower quality than I and P frames). And if you want faster encoding turn down the Encoding Quality settings (set both Motion Search Precision and VHQ mode to 0). In target quantizer mode this will have no effect on quality, only the file size and encodins speed.

Oh, and be sure to enable 2 threads!

[^xRun^]

Are you talking about B-VOPs ? Turn that off?

[jagabo]

Yes.

Oh, and you need one of the multithreaded v 1.2 builds to use multithreading:

https://www.videohelp.com/forum/archive/xvid-1-2-multicore-t337030.html

[^xRun^]

Ok, that increased the data for this short clip from about 200MB to about 390MB and increased the speed a lot... but some motion artefacts appeared... a little "tearing" to put a word on it, so I'll just set quantizer to 1 and be happy with that.

Edit: I'll keep motion search, but turn off B-VOPs.

[jagabo]

Tearing isn't a problem with the encoding. It's the playback. You can get most of the speed without sacrificing too much file size with the two motion search precision option set to 1.