RC3 H264 encoding quality worse than 0.86i with low bitrates

[thomasferre]

Hi

I am happily using VLC for several years to do live H264 multicast streaming.

I used to use 0.86i with no pb with my personnal H264 encoding parameters.

I upgraded to new RC3.

The new X264 library with RC3 is using a lot less CPU than the 0.86i (which is a good thing) but produces poorer quality with low bitrates (<=512 kb/s).

It never happened with 0.86i with low bitrates.

Also this pb never happen in RC3 with higher bitrates.

After some tests, it seems that this pb appears in RC3 ONLY with bitrates <900 kb/s.

Does anyone met the same pb ?

Thanks.

Regards

[Lotesdelere]

Try to use a higher -subme

There were 7 levels before but there are 9 now so the scale has changed.

[thomasferre]

Thanks

With a value of 7 instead of 5, the pixelisation pb disappears with bitrate between 512 kb/s and 1 mb/s.

But I still got the pb with bitrate <512 kb/s

[thomasferre]

Sorry, I am back again ...

Increasing the subme to 7 or 8 or 9 with 1.0 RC3 improves encoding quality with bit rates between 512 kb/s and 1000 kb/s.

But the pb remains with VERY low bitrates.

For example, with a 384 kb/s H264 stream, VLC 0.86i produces a much better quality image with the same parameter (except the subme at 7 for 0.86i and at 9 for 1.0 RC3).

Is there any other parameter that I can change in 1.0 RC3 H264 to improve it ?

You can do the test :

try to encode with H264 at 384 kb/s with 0.86i and 1.0 RC3 and you will see a BIG quality difference.

Thanks for your help.

Regards

[Lotesdelere]

Sorry but I don't have much experience about H264 streaming, I'm more about conversion so I'm not sure which parameters are good to use for streaming.

Let's hope a dev will read this thread but maybe you'll have more chance and answers on the VLC IRC channel: #videolan on irc.freenode.net.

please join #videolan on irc.freenode.net. It might take a while before we answer, and please keep in mind that most of us are in European timezones.

[thomasferre]

Hi

Just to show you the pb :

I am using the same X264 configuration with VLC 1.0 RC3 and VLC 0.86i.

As you can see, with a 384 kb/s bit-rate, there is a BIG quality difference ...

VLC 0.86 i :


VLC 1.0 RC3 :


Once again, the quality difference is only happening with very LOW bitrates (<512 kb/s).

With high bitrates, X264 encoding with 0.86i and 1.0 RC3 are the same quality.

Thanks for your help.

[thomasferre]

Nobody is interessed by this subject ?

[The DJ]

use a higher subme setting. The scale of the x264 subme setting has changed between the x264 version included in 0.8.6 and the x264 version used by 1.0.0

[thomasferre]

Already tried with 7,8 and 9 subme.

Same pb.

[Lotesdelere]

You should post all of the settings you are using with both versions so we can check what is going wrong.

[thomasferre]

Hi

I have posted my whole X264 configuration here :

viewtopic.php?f=4&t=60871

I am using the same X264 configuration with 0.86i and 1.0 RC3

I know that subme values have changed from 0.86i (1-7) to 1.0 rc3 (1-9).

I tried with the best subme values 9 with 1.0 RC3.

Still poor quality with 384 kb/s.

You can do the test : try to encode H264 at 384 kb/s with 0.86i and 1.0 RC3 with the same X264 configuration

There is a BIG quality difference.

Thansk for your help

[Lotesdelere]

Post both full command lines you are using.

[thomasferre]

I am using the same VLC bach file with 0.86i and 1.0 RC3 :

start vlc.exe dshow:// :dshow-vdev="Osprey-100 Video Device 1" :dshow-fps=25.000 :dshow-adev="SigmaTel Audio" :sout=#transcode{vcodec=h264,vb=384,scale=1,acodec=mp4a,ab=64,channels=1,samplerate=44100}

My X264 configuration is in this post : viewtopic.php?f=4&t=60871

Thanks for your help.

You can try to the test :

live H264 encoding at 384 kb/s with 0.86i and 1.0 RC3

0.86i is much better with low bitrate (same quality with high bitrates >1mb/s).

[thomasferre]

Hi

I have also experienced that X264 transcoding with 1.0 is VERY SENSIBLE to capture video noise from a camera (such as lack of light in a room).

With a little video noise, 1.0 RC3 produces a much poorer quality than 0.86i, event at high bitrates (>1 Mb/s).

I wanted to use mp4v with 1.0 but it is not available anymore.

So I went back to 0.86i which was, according to me, the last version with a good transcoding capacities.

0.9X and 1.0 RC X are no good for transcoding.

Does the VLC transcoding team agree with that ?

Thanks.