H264.mov - forced CBR ?

[kisielo]

Hi,
I have an animated cartoon digitalized from PAL DIGIBETA tape onto the mov file with the ProRes 422HQ codec.
It is an old cartoon called PEPA: http://www.youtube.com/watch?v=DCWHh_mZogE

The initial video bitrate is variable bitrate @24.5 Mbps.
I need to recompess the file into h264 with the bitrate of 6-8 Mbps.
I used Mpegstreamclip and Handbreak but I can't get the required bitrate.

In Handbreak, even if I choose constant quality @RF:0 (lossless), the output file is around 2 Mbps.
In mpegstreamclip I select H.264 Multi-pass restricted to 8 Mbps and optimized for download, I get the same output bitrate of around 2 Mbps.

I have also tried FFMpeg for Mac, with the Force Constant Bitrate option enabled and the output was the same as above.

Would anyone here know of a way to create a h264 video in a mov wrapper which would allow to set a constant bitrate of a choice?

Please help!

All the best!

[jman98]

I have also tried FFMpeg for Mac, with the Force Constant Bitrate option enabled and the output was the same as above.

Does this mean you are doing it on a Mac? If so then your post should have gone to our Mac forum as you need Mac specific help. Most of us use Windows here so anything that has to be done on a Mac really needs to go in the Mac forum. For example, I'd suggest using MeGUI but it only runs under Windows.

[kisielo]

Hi there
I was totally not aware that there is a MAC specific forum here. Please excuse my mistake and thank you for suggesting MeGUI. I work on both systems so this might just help. I will give it a try!

I am moving my post to MAC related forums.

Kind regards
Andrzej

[jagabo]

When a video doesn't have much detail encoders often can't reach higher bitrates. The fact that you couldn't get the bitrate you wanted with CRF=0 indicates that is the condition you have. But I find it hard to believe that video captured from any tape source would have that problem unless you've run very heavy noise filtering.

There are some things you can do that will force the encoder to use more bitrate, even in this situation. Disable b-frames and use short GOPs. In x264 that means set the minimum GOP size to 1, the maximum GOP size to small values like 1 to 10. This won't improve the "quality", just raise the bitrate.

[kisielo]

Hi,
I am almost positive that my problem is caused by the low complexity of the video. I have just tried your suggestions and it seems that it helped!
On MAC i am using iFFmpeg and I have disabled the b-frames and set the minimum GOP to: 2 (thats the lowest setting available there) I can't find any settings for max GOP. There are also options like:

Closed GOT - this is disabled
Strickly Enforce GOP soze - this is disabled
Auto set GOP size - this is disabled
Frames to look ahead - this is set to 40

The output file has now exactly 8Mb/sec so it seems that your advise did the trick!
Thank you so much for your help!

[kisielo]

I owe you a beer man!

[jagabo]

I recommend you set the GOP size to the highest value that will achieve the bitrate you want. Setting it too low will give you reduced quality. Though I don't understand why you need 8 Mb/s when 2 Mb/s will do.