ProRes 422HQ to H264 - BITRATE PROBLEM

[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 have a solution to this problem?

All the best!

[_Al_]

Perhaps 2Mbit/s is more than enough? Same colors all over picture, no gradients.

[kisielo]

Hi there,
2Mbit/s would be more than enough although the VOD platform which I am preparing the video will not accept any files with lower bitrate than 6Mbit/s.

[_Al_]

Use CBR mode (constant bitrate), editing softwares like Premiere or Vegas will encode like that, even their light versions (Vegas Platinum or Premiere Elements), Vegas trials are for free. Maybe there is some free utility that can load ProRes and encodes CBR as well like ffmpeg (not straight forward to do it first time). Or even some free converters that are around even here on videohelp database.

Or you can use handbrake and VBR mode (variable bitrate), where you set average as 7-8 Mbit. It will encode in two passes. But there might be some bitrate fluctuations anyway, you can try that.

[kisielo]

In Handbreak, even if I choose constant quality @RF:0 (lossless), the output file is around 2 Mbps.
FFmpeg with CBR ON gives the same output. I need a software or a specofic setting for ffmpeg
which will somehowe ignore the low complexity of the video and will create a h264 video with a desired bitrate.

[poisondeathray]

I thought you already solved this ?

https://forum.videohelp.com/threads/355232-H264-mov-forced-CBR?p=2233959#post2233959


In ffmpeg, you would set -g is the same thing as --keyint in x264cli. e.g. set -g 1 for maximum gop length of 1 (or some other value) ,

[_Al_]

In Handbreak, even if I choose constant quality @RF:0 (lossless), the output file is around 2 Mbps.
FFmpeg with CBR ON gives the same output. I need a software or a specofic setting for ffmpeg
which will somehowe ignore the low complexity of the video and will create a h264 video with a desired bitrate.

If ffmpeg is not working for you, you can try other suggestions I mentioned before. Try outs of Vegas for example. CBR works there , You set 6.5 Mbit/s and you get 6.5 Mbit/s.

And again 2pass VBR might work for you also, I do not have Handbrake here, but I'm sure there is 2pass VBR in options there. You set average bitrate for 7Mbit. Try it.

[Cornucopia]

Hi there,
2Mbit/s would be more than enough although the VOD platform which I am preparing the video will not accept any files with lower bitrate than 6Mbit/s.

There's the rub. And one I would guess that is faulty. Are you really sure? VOD sites/services WANT to economize on bitrate!
Perhaps with more info...

Scott

[kisielo]

The VOD platform for which I have to compress has a specific bitrate requirements and it's bet. 6-8Mb/sec. I know that they will further comprees the files down to a really poor quality but they will not accept anything outside their specs. They have some sort of an internal software developed which does a check all the submited files. If the bitrate goes out of range the file is autmatically rejected.

2 pass vbr does not do the trick. I have tried this alreqdy in Handbreak, Mpegstreamclip and Compressor 4. The output file is always around 2Mb/sec - nomatter how high I set the bitrate in the settings.

[Cornucopia]

Well, if that's how they want it..
Then I would agree with _Al_'s suggestion and just do CBR. Quick and easy, one pass, no fuss no muss. It's not like you would have a bitrate deficiency somewhere in the file, by the sound of it.

Scott

<edit> if ffmpeg won't be corralled into doing cbr, use Compressor. I know it can do cbr. If you cannot do it there, there must be something wrong with your settings...(show us)

[kisielo]

Hi,
the file size is not a concern here, it's the required bitrate. I have tried Compressor but I can't find a CBR option in it's H264 settings. The only option is to restrict data rate to a specific value. I have tested all possible options with single and multi pass and both optimized for streaming and download. In all scenarios even if I set the required bitrate way over my needs the output file is around 2Mb/sec. It seems to me that there is no way to compress with CBR in Compressor.

It is a bit strange with the iffmpeg as when I use it's CBR setting on some other video files with more complex content, it works perfectly and after compression I get the exact bitrate as specified. If I try to compress the PEPA cartoon the output file has a much lower bitrate than expected.

[jagabo]

the file size is not a concern here, it's the required bitrate.

For a given run time they are the same thing.

File size = bitrate * running time

I already told you how to push the bitrate up in your other thread. Another thing you can do is add noise to the video. That will eat up bitrate. But it may also reduce the image quality.

[kisielo]

Hi,
I was too entusiastic over the wekend, jagabo. I have tested the wrong file with the settings which you suggested. The PEPA video keeps fighting and I am unable to get the bitrate higher than 2Mb/sec. Adding extra noise to the picture would be my last choice as this is an old cartoon and it's already pretty noisy.

Here is the rundown of all the settings which I used in iffmpeg: http://imgur.com/4kB1Fno
Ant the output file in iMEdia HUD looks like this: http://imgur.com/9NRemjY
The nominal bitrate is what I have set: 8Mb/sec but the bitrate value is only 1971 Kbps

[poisondeathray]

It's typically done with "padding" or "filler bytes" at the muxing stage . e.g. when the VOD provider mutiplexes it into the transport stream before broadast

For x264, you would set ( bitrate = maxrate = bufsize ) , and set --nal-hrd cbr, outputting a raw avc stream.

e.g

x264 --bitrate 8000 --nal-hrd cbr --vbv-maxrate 8000 --vbv-bufsize 8000 -o filler.264 input.ext

In this example, --keyint 0 --crf 0 yielded a stream less than 1Mb/s , but with CBR padding, it reaches the specified bitrate (8Mb/s in this example).

If you multiplex without CBR mode, the filler bytes typically will be stripped. For example, If you take filler.264 and muxed it with "normal" muxers , you will notice the filesize drop much smaller than the crf0 file. In fact if you notice the zip filesize is tiny - that's already evidence of "filler" bytes (I zipped it up because this message board doesn't accept raw .264 files). You can use CBR muxing in something like tsmuxer.

There are applications based on x264 that can do this all for you, check out open broadcast encoder (still in development)
http://www.ob-encoder.com/

Normally this isn't required, because the padding is added at the broadcast end, so I would triple check (again) to see if this is really required...

[kisielo]

Hi 'poisondeathray'
I have contacted the VOD platform once again and explained the situation. They accepted lower bitrate in this case. They did some tests at their end with one episode which I have delivered to them in prores and they had worse results than my own in regard to bitrate.

Thank you for the suggestions. My skills in the field are not that good yet, I am still learning. I've heard about open broadcast encoder but I don't think that there is any GUI for it yet and I am not yet ready to use the command line.

I have thied tsmuxer and it works. In GENERAL tab I can choose the value of Mux CBR but it can only mux into TS or M2TS and I need a .mov container at the end. Is there a way to change containers after muxing to ts file?