Doom9's Forum - View Single Post - x264 and BD (part 2)

mp3dom · 7th May 2011, 22:22

Ok, after my previous post made about six months ago I've re-run a test with the latest version of x264 (rev.1947) to see if improvements have made this encoder high-quality 'stable' for BD encoding. While I've seen some improvements, I still continue to have some 'old' problems that I cannot actually resolve. So I'm asking for both suggestions and wish this post can be useful to someone.
Source/encoded file can be provided to developers if they need it (the files are huge so I need some time to upload)
First of all, this is the command-line used:

Code:

x264.exe --profile high --preset veryslow --tune film --slow-firstpass --keyint 24 --bframes 3 --b-pyramid strict --open-gop --ref 3 --slices 4 --bitrate 37000 --vbv-maxrate 40000 --vbv-bufsize 30000
--weightp 1 --merange 32 --no-fast-pskip --no-dct-decimate --videoformat ntsc --colorprim bt709 --transfer bt709 --colormatrix bt709 --nal-hrd vbr --pic-struct --sar 1:1 --level 4.1 --bluray-compat

I think the parameters are quite good (quality-wise) and bitrate is very high (37 Mbps average). The average qp of the whole encode is near 10.
Source is japanese animation as it's the only footage that I'm working on.
The images are a closeup of the source, zoomed 2x and enhanced to show better the problem for those who have uncalibrated monitor.The images are divided in:
top left: original source
top right: original enhanced (brightness/contrast boosted)
bottom left: x264 original encoded
bottom right: x264 original encoded enhanced (boosted)

This frame is encoded as P frame by x264. There's a bad grain retention and also the black border (it's and edge) shows some artefact.

Here there's some bad grain retention on the lower edge of the orange line but the biggest problem here is the strange artefact that you can see pointed with the white arrow

All white arrows points to artefacts or not-so-good grain retention

Here there's no need to do an enhanced version as it's all visible. The frame was encoded as a B frame (but also previous/forward P/B frames shows the same problem). As you can see, there's some sort of 'ringing' around the contrast line. The image it's a white circle with a faded aura surrounded with black background. It's almost still for a small duration of time (about 10 frames). Also the gradient is visibly less smooth than original. The bitrate used for this frame is very low (there's a lot of black around and the circle is pure white, so it's quite normal) but some macroblocks here have a qp of 25 or more which I think is a bit too much.

Suggestions or requests?

P.S: I would like to not damage the thread with a 'war' between x264 and other pro-encoder.

7th May 2011, 22:22	#1 \| Link
mp3dom Registered User Join Date: Jul 2003 Location: Italy Posts: 1,135	x264 and BD (part 2) - asking for suggestions Ok, after my previous post made about six months ago I've re-run a test with the latest version of x264 (rev.1947) to see if improvements have made this encoder high-quality 'stable' for BD encoding. While I've seen some improvements, I still continue to have some 'old' problems that I cannot actually resolve. So I'm asking for both suggestions and wish this post can be useful to someone. Source/encoded file can be provided to developers if they need it (the files are huge so I need some time to upload) First of all, this is the command-line used: Code: x264.exe --profile high --preset veryslow --tune film --slow-firstpass --keyint 24 --bframes 3 --b-pyramid strict --open-gop --ref 3 --slices 4 --bitrate 37000 --vbv-maxrate 40000 --vbv-bufsize 30000 --weightp 1 --merange 32 --no-fast-pskip --no-dct-decimate --videoformat ntsc --colorprim bt709 --transfer bt709 --colormatrix bt709 --nal-hrd vbr --pic-struct --sar 1:1 --level 4.1 --bluray-compat I think the parameters are quite good (quality-wise) and bitrate is very high (37 Mbps average). The average qp of the whole encode is near 10. Source is japanese animation as it's the only footage that I'm working on. The images are a closeup of the source, zoomed 2x and enhanced to show better the problem for those who have uncalibrated monitor.The images are divided in: top left: original source top right: original enhanced (brightness/contrast boosted) bottom left: x264 original encoded bottom right: x264 original encoded enhanced (boosted) This frame is encoded as P frame by x264. There's a bad grain retention and also the black border (it's and edge) shows some artefact. Here there's some bad grain retention on the lower edge of the orange line but the biggest problem here is the strange artefact that you can see pointed with the white arrow All white arrows points to artefacts or not-so-good grain retention Here there's no need to do an enhanced version as it's all visible. The frame was encoded as a B frame (but also previous/forward P/B frames shows the same problem). As you can see, there's some sort of 'ringing' around the contrast line. The image it's a white circle with a faded aura surrounded with black background. It's almost still for a small duration of time (about 10 frames). Also the gradient is visibly less smooth than original. The bitrate used for this frame is very low (there's a lot of black around and the circle is pure white, so it's quite normal) but some macroblocks here have a qp of 25 or more which I think is a bit too much. Suggestions or requests? P.S: I would like to not damage the thread with a 'war' between x264 and other pro-encoder. Last edited by mp3dom; 7th May 2011 at 22:31.