FCS3 bit rates

[Gary Nattrass]

I have been doing some testing and have loaded a 15 sec AVC Intra 100 clip into FCS3 at all the P2 options for bit rates.

Native shows the correct bit rate of over 100mbs but all the others inc pro res HQ show far lower bit rates.

I then put the native AVC clip on the timeline and it set the system at pro res HQ which is what I would expect but when I do an export to file the bit rate is also very low at 22.4mbs.
This did not happen in FCS2 am I missing something or does FCS3 now compress everything? I havent changed any settings and let FCS3 adjust the timeline to the AVC native clip.

Here are some stats:

Original native AVC clip import to FCS3:
General / Container Stream # 1
Total Video Streams for this File -> 1
Total Audio Streams for this File -> 4
Video Codecs Used -> ai12
Audio Codecs Used -> PCM / PCM / PCM / PCM
File Format -> MPEG-4
Play Time -> 15s 240ms
Total File Size -> 212 MiB
Total Stream BitRate -> 117 Mbps
Video Stream # 1
Codec (Human Name) -> ai12
Codec (FourCC) -> ai12
Frame Width -> 1 920 pixels
Frame Height -> 1 080 pixels
Frame Rate -> 25.000 fps
Total Frames -> 381
Display Aspect Ratio -> 16/9
QF (like Gordian Knot) -> 2.193
Video Stream Length -> 15s 240ms
Video Stream BitRate -> 114 Mbps
Video Stream BitRate Mode -> CBR
Video Stream Size -> 206 MiB (97%)
Date of Original Encoding -> UTC 2009-09-02 15:23:13

Export in pro res HQ:
General / Container Stream # 1
Total Video Streams for this File -> 1
Total Audio Streams for this File -> 1
Video Codecs Used -> apch
Audio Codecs Used -> PCM
File Format -> MPEG-4
Play Time -> 15s 240ms
Total File Size -> 40.7 MiB
Total Stream BitRate -> 22.4 Mbps
Video Stream # 1
Codec (Human Name) -> apch
Codec (FourCC) -> apch
Frame Width -> 1 920 pixels
Frame Height -> 1 080 pixels
Frame Rate -> 25.000 fps
Total Frames -> 381
Display Aspect Ratio -> 16/9
QF (like Gordian Knot) -> 0.402
Video Stream Length -> 15s 240ms
Video Stream BitRate -> 20.8 Mbps
Video Stream BitRate Mode -> CBR
Video Stream Size -> 37.8 MiB (93%)
Date of Original Encoding -> UTC 2009-09-03 06:34:04

[Gary Nattrass]

Just did the same test from AVC native import at over 100mbs to pro res HQ via compressor and it is showing the same result a pro res file with less than 30mbs bit rate.

[Tim Dashwood]

If you are transcoding to ProRes then the bitrate is locked to that particular ProRes codec - it doesn't care what the source was, although I think the bitrate varies with resolution.

If you import in AVCIntra100 native (preference pane in Log & Transfer) then it should still be 100mbps. FCP will report that in MB/s, which should be around 12MB/s.

The odd thing is that you can natively import AVCIntra but there are no AVCIntra sequence presets, so it seems the AVCIntra codec is really just a decoder and you still need to use prores for your sequence.

In you second example you have exported in an MP4 container so who knows what's going on when that happens - it says the codec is "apch." Is that Apache codec? Can you just export a Quicktime of ProRes HQ and check the bitrate of that?

[Tim Dashwood]

BTW, these are the bitrates I've gotten with the new ProRes Codecs with 1920x1080i60 clips.
http://www.dvinfo.net/conf/attachmen...sity_test2.png

224 mbps ProRes 4444
224 mbps ProRes 422 HQ
112 mbps ProRes 422
90 mbps ProRes 422 LT
45 mbps ProRes 422 Proxy

That's pretty good compared to Uncompressed 8-bit 422 at 950 mbps!

[Gary Nattrass]

Hi Tim and thanks for your reply.

The native AVC 100 went in OK at around 100mbs and when I dropped it onto the time line it changed the sequence to Pro Res HQ.

I then did a quicktime export (no sequence changes just straight back out) and the bit rate is less than 30mbs as shown on the 2nd readout above.

When I transcoded the AVC to Pro res HQ it also showed a bit rate of less than 30mbs.

When I used to do the same processes with FCS2 I got bit rates at over 100mbs for straight pro res and HQ was much more.
I dont understand why this has now changed in FCS3

[Gary Nattrass]

Just checked the import bit rates on the sequence screen FCS3 and they are:

Apple AVC-intra 100 1080p25 13.9MB/S
DVCPRO HD 1080p25 14.1MB/S
Apple Pro Res 422(Proxy) 1.7MB/S
Apple Pro Res 422(LT) 2.2MB/S
Apple Pro Res 422 2.5MB/S
Apple Pro Res 422 HQ 2.8MB/S

Are they correct Tim?

Also I repeated things with just one clip to make it simple and also looked at the file sizes.

So when I look at the data for the native imported 15 sec AVC intra 100 clip it is 212.3mb
When I look at the same clip but transcoded to Pro Res 422 HQ in log and transfer it is only 43.5mb
Putting the AVC intra 100 native clip on the timeline (changes it to pro res HQ) and export to quicktime at pro res HQ the file size is 40.7mb

Thanks in advance for any insights, I may put FCS2 back on one of my machines just to check I am not totally going bit rate mad!

[Andy Mees]

Gary, don't forget that ProRes is a VBR codec ... the actual bit rate and resulting file size for any given clip may vary massively dependent on the actual visual content of the source. Is it possible you're using a less than real world representative source clip for your tests?

[Gary Nattrass]

Originally Posted by Andy Mees

Gary, don't forget that ProRes is a VBR codec ... the actual bit rate and resulting file size for any given clip may vary massively dependent on the actual visual content of the source. Is it possible you're using a less than real world representative source clip for your tests?

Thanks Andy that is a good point and may be right as I am using a 15 sec clip of colour bars.

I had a look at some old projects imported as pro res 422 and they are showing a bit rate of around 15MB/S in the FCP window.
I will re-import some of the same media and see if it is any different.

[Gary Nattrass]

DOH! what a dumbo I am for using 15 secs of static colour bars to do codec tests with.

Sorry for all your trouble guys but as Andy correctly pointed out it was the VBR that was giving me strange results.

Ive done the same tests on some moving pictures and what I am now seeing is correct.

Thanks for guiding me out of the woods I should really stick to audio in the future.