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virus · 11th January 2004, 11:55

Hi!

I've tried out both VP6 6.0.9.2 and 6.1.0.2 and I'd like to share my views with you. I made some 2-pass encodings (clips from 40 seconds up to 6 minutes long) at 512x288 @ 25 fps (from DVD sources) with datarate between 650 and 800 kbps (~1 CD rips) and I compared it with XviD 1.0-beta2.

The output was fine. I think VP6 is very good at matching the colours of the source. Instead in some XviD clips there was a slight shift to red (not only on faces) and the original colour range was lost. Same (and maybe worse) for DivX5. Also, under 700 kbps (that's < 0.2 bpp) VP6 wins even for overall quality. I did my tests with no spatial/temporal resampling and min quantizer set to 4. I'm just wondering how a codec with no B-frames can reach such a performance. IMHO from a purely technical standpoint VP6 is a very interesting codec.

Also, I did a test with 120 KB/s rate (983 kbps, 0.266 bpp) and compared VP6 to XviD to dig deep into the classic "XviD retains more detail". This turned out to be true, but only with MPEG quantization, as I expected. XviD w/ H.263 looked quite similar to VP6.
So I think a different quantization should be embedded in VP6 for higher bitrates (> 0.2 bpp). VP6 is optimized for low bitrates but it doesn't scale well at higher rates. You add a lot of bits and get almost nothing. Lowering the min quantizer to 2 seems to help, but not that much.

Now, about the codec flaws...:
1) I'm going to strongly support the request (already made) of a Registry hack to set the default bitrate (in kilobits please!). I use DVDx 2.2 which has no GUI to enter the value. And with an integer KB value you've only a granularity of 8192 bps, not really the best...
2) sadly, with 2-pass I got oversized files up to 3% for 40-seconds clips, and even 0.5-0.6% on a 6-minutes clip. This is too high compared to XviD/DivX, and not so good for fitting a movie into a CD.
3) 2nd pass best quality is quite slow (got 7 fps on a P4 2.4GHz with VOB decoding/resize overhead, and 9-10 from uncompressed source)
4) where is the "General" profile you talk about in your site?

Also, I found a badframes.stt file in VDub directory, generated by version 6.1.0.2 (got a lot of badframes.stt with 6.0.9.2, now only one... guess we're improving

)

Overall, I think that VP6 is a very good product.
If On2 manages to improve it (oversize/interface especially), it may even be excellent.
I look forward to newer releases.

11th January 2004, 11:55	#6 \| Link
virus Senior n00b Join Date: Jan 2004 Location: Italy Posts: 446	Hi! I've tried out both VP6 6.0.9.2 and 6.1.0.2 and I'd like to share my views with you. I made some 2-pass encodings (clips from 40 seconds up to 6 minutes long) at 512x288 @ 25 fps (from DVD sources) with datarate between 650 and 800 kbps (~1 CD rips) and I compared it with XviD 1.0-beta2. The output was fine. I think VP6 is very good at matching the colours of the source. Instead in some XviD clips there was a slight shift to red (not only on faces) and the original colour range was lost. Same (and maybe worse) for DivX5. Also, under 700 kbps (that's < 0.2 bpp) VP6 wins even for overall quality. I did my tests with no spatial/temporal resampling and min quantizer set to 4. I'm just wondering how a codec with no B-frames can reach such a performance. IMHO from a purely technical standpoint VP6 is a very interesting codec. Also, I did a test with 120 KB/s rate (983 kbps, 0.266 bpp) and compared VP6 to XviD to dig deep into the classic "XviD retains more detail". This turned out to be true, but only with MPEG quantization, as I expected. XviD w/ H.263 looked quite similar to VP6. So I think a different quantization should be embedded in VP6 for higher bitrates (> 0.2 bpp). VP6 is optimized for low bitrates but it doesn't scale well at higher rates. You add a lot of bits and get almost nothing. Lowering the min quantizer to 2 seems to help, but not that much. Now, about the codec flaws...: 1) I'm going to strongly support the request (already made) of a Registry hack to set the default bitrate (in kilobits please!). I use DVDx 2.2 which has no GUI to enter the value. And with an integer KB value you've only a granularity of 8192 bps, not really the best... 2) sadly, with 2-pass I got oversized files up to 3% for 40-seconds clips, and even 0.5-0.6% on a 6-minutes clip. This is too high compared to XviD/DivX, and not so good for fitting a movie into a CD. 3) 2nd pass best quality is quite slow (got 7 fps on a P4 2.4GHz with VOB decoding/resize overhead, and 9-10 from uncompressed source) 4) where is the "General" profile you talk about in your site? Also, I found a badframes.stt file in VDub directory, generated by version 6.1.0.2 (got a lot of badframes.stt with 6.0.9.2, now only one... guess we're improving ) Overall, I think that VP6 is a very good product. If On2 manages to improve it (oversize/interface especially), it may even be excellent. I look forward to newer releases.