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Data rate in Final Cut Pro 7 browser window
  • KittihawkKittihawk

    I've seen this topic addressed before but as a Mac user it is unsettling to see that a patch appears not to change the data rate from the default factory setting when converted to Apple Pro Res using log and transfer in FCP7. In most cases a bitrate of 13-14mbs is reported in the browser window under the data rate column. One answer given is that this is because it is converted to Pro Res - however, I have several other sources of Pro Res (e.g. from various high spec video cameras such as Sony EX1 or even Red) that report much higher data rates in that same column but are still Pro Res.

    So this suggests a couple of things might be happening:

    1) Something is causing FCP7 not to report the correct data rate for AVCHD files converted to Pro Res. This seems unlikely as the data rates for other media and even Pro Res vary between 13-160 ish mbs, mostly as you'd expect according to camera spec. 2) The log and transfer conversion of AVCHD to Pro Res is somehow limited in FCP7 and is not actually "allowed" at the higher bit rate due to something in the programming. This is the most disturbing because it means that the extra bit rate is indeed being lost. Basically this boils down to 'the patch doesn't work in FCP7'

    Anybody made further progress on this?

  • 6 Replies sorted by
  • KittihawkKittihawk

    OK the 'white paper' on Apple ProRes codecs (below) goes some way to explaining what's going on, but if you look at the final table of 'Target data rates' for Apple ProRes 422, in this Apple published document, then you will see that all of the data rates should be higher than the approx. 13MBS actually seen on log and transferring high data rate hacked, or even native, GH2 footage in FCP7.

    The paper explains that the data rate of a particular Apple ProRes version depends on the codec, the frame rate, and the frame size (so is not exactly related to the data rate of the source). What is going on is a clever compression of the media so that it can be easily edited on an average spec system. However, I don't think that entirely explains the unexpectedly low date rate seen on the conversion of GH2 native and hacked footage.

    http://images.apple.com/support/finalcutpro/docs/Apple-ProRes-White-Paper-July-2009.pdf

    I know I'm missing something here - but what?

  • htinlahtinla

    Pardon me for taking your technical discussion and dumbing it down, but I wouldn't worry about metadata things like that. The bottom-line subjective picture quality is what matters most. If it looks good to your eyes (and at least one other person), then nothing else matters. But if it helps, I find that log & transfer gives me ProRes files that maintain the quality of the hacked GH2 files. This is my subjective opinion that's not based on extensive pixel-peeping. I haven't noted what data rates FCP is reporting, but the final ProRes file sizes are always around 3 to 5 times larger than the source file, so I know my transcodes are definitely not over-compressing anything, if that's what you are concerned about.

  • driftwooddriftwood

    If it concerns you, you may want to change/trick the level of the AVCHD profile - remux to a higher profile level with proggies like tsMuxeR that allow higher bitrate AVC interp in older editors/or prores converters. e.g. This may perform better in an FCP7 ingest.

  • KittihawkKittihawk

    The issue is this - the broadcast threshold for acceptance of video by BBC, Discovery, Nat Geo etc is set at 50mbps - under this value and it is not accepted for broadcast (although some allow a quota such as 15% of the total show). This is why cameras like the Sony EX1 need to have a Nanoflash box added to bump the data rate to 50 or 100mbps.

    It seems that the bit rate reported by Final Cut 7 is in fact a more accurate assessment of quality as it takes into account multiple things such as frame size and frames per second - in other words just upping the bitrate doesn't actually cut the mustard by itself. That is why, if I can get FCP to report higher bitrates in Final Cut 7, I would be reassured that the patches are actually 'objectively' doing something. As it is FCP 7 is not differentiating between the patched and unpatched GH2 media.

    Thanks Driftwood for the suggestion - I will give it a try if I can figure it out.

  • vicharrisvicharris

    This is funny because I thought the same thing when I first started editing HVX200 footage. I believe it never showed the bit rate being over 13 or so after I logged it in so I figured it was just something weird FCPwas doing and blew it off. I never had a problem with delivered footage from anyone. I just told them what it was shot on that was good enough for them!

  • rocknrollchefrocknrollchef

    Hello:

    Newly-hacked GH2 noob here, would love some experienced input on compression, files sizes, etc. transferring the hacked footage with FCP "log & transfer." I, too noticed the GH2 footage ingested with the "log & transfer" function was knocked down to approx. 13mbs and Pro Res 422 formatted. What gives? Doesn't that defeat the purpose of the higher bitrate/resolution? If what Kittihawk is saying about BBC, Discovery etc. having minimum requirements of 50mbps acceptance threshold is true, what's the solution here? Find a way to increase the bitrate with the edited piece? And was exactly is meant by "change/trick the level of the AVCHD profile?"

    THANK YOU!

    chef

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