QT export, bit rates, etc.

Discussion in 'Digital Video' started by ggulliver, Jul 10, 2013.

  1. macrumors member

    Jan 22, 2008
    I have some home movies which originated on a HD cam and which have been edited with Final Cut then saved as mov files.

    As they're large (typically 1gb per minute for 1920x1080), I want to convert them to a more convenient file size (probably 10mb per minute) whilst keeping the frame size.

    Is QT export as H.264 mp4 the sensible option?
    If so at what bit rate?
    Is there any advantage/disadvantage in changing from mov to mp4?
  2. macrumors 6502a

    Mar 6, 2007
    For home movies, where the quality is worth keeping, I'd recommend 10,000 to 16,000Kb/s depending on how "busy" the video is.

    (10MB/m would be 1,365Kb/s, which would look terrible for 1920x1080 video.)
  3. thread starter macrumors member

    Jan 22, 2008

    The data rate thing confuses me; I'd based my thinking on downloaded movies - which typically have rates of 1700-2200kbps and a file size of 1.5gb for a 90-minute runtime.

    With your suggested rates, won't the filesize be about 2.8-3.5gb? That seems high for a 30-minute runtime but if it needs to be to maintain quality then ok... but I just don't understand how the previously mentioned movies seem to be decent quality at lower rates/sizes.
  4. macrumors regular

    Dec 11, 2012

    You cant judge data rate on downloaded movies.. those are ripped by people who dont truly understand what theyre doing.

    If you are worried about file size.. then get bigger drives.. trying to keep it looking good at 1080p will be sorta big.. besides.. I work on broadcast spots.. a 30 sec 1080p spot can be 2gb! 2k and 4k.. forget.. but we have massive servers..

    Sorry but you will not get 10mb per minute at 1080p.. it will look like garbage.

    anyway.. try 6500-7500 kbp/s bit rate.. h264 is ok.. are you keeping the original media? if not you may want to reconsider how you want to keep the media stored.

    How much footage do you have?
  5. thread starter macrumors member

    Jan 22, 2008
    That's not for me to say. What's clear though is that they're decently watchable.

    There's a point of practicality here - cost.

    That figure is what the downloads have, and they're ok quality.

    Thanks, I'll try that rate. I'm not keeping the originals - I just want to get them off the cam, edit and save for viewing/long-term keeping.

    Currently, not much - but of course it'll grow.

    I'm not trying to be awkward here - simply trying to understand how the rates of the downloaded items can be so low.
  6. macrumors regular

    Dec 11, 2012
    Just so you know.. I've been a pro editor for 10+ years.. I deal with files, compressions, trancodes, etc daily.. I'm here to help out as best as I can!

    back to your questions:

    It has to do with the codecs that are used to compress the files..

    Quicktimes, .mp4s, .mpeg, wmvs files can be created dozens of ways.. some have huge data rates, others are small.. its based on usage..

    example.. Broadcast files have data rates of 220 mbps and up, with 170 mbps being the low end..

    compare that to a movie download.. maybe 6mbps.. trust me.. a 1080p movie that is 10 mb per minute (file size) is garbage.. the 1080p I download are usually around 4gbs+, that is 33 mb per minute.. they look decent.. the better ones I have are more like 15gbs per movie, which is 125 mbs per minute.

    Speaking of.. movie rips are usually compressed more so people can download them quickly..

    Now, what is the exact format of these movies? You said HD cam, but are they AVCHD? Mpeg or quicktime files? good info to know to help you.

    Heres a test.. do you have mpeg streamclip?


    Its faster then FCP..

    throw a file in at and choose H264 as the codec.. but dont constrain the bit rate.. leave it on auto

    let it rip.. compare that file to the original media.. should look pretty darn good.. But if the file size is too large.. then throttle the data rate down.

    You can also export right out of FCP this way, just dont set a data rate.

    This is to give you a bench mark as to how they look, and how large the files are.

    And honestly, storage is cheap.. a little external 1tb is $100.. these are your home movies right? Then you should store them at good quality, and always hold on to the original tapes if you are shooting on tape... or as I do, keep the original footage on a drive.

    Attached Files:

  7. thread starter macrumors member

    Jan 22, 2008
    Thanks, I appreciate your help.

    And I understand/accept your points on bit rates etc, and I'm not here to argue... but am still puzzled by the quality/size ratio of those downloaded movies - which simply don't support your point of 'you will not get 10mb per minute at 1080p... it will look like garbage'.

    It simply doesn't (look like garbage). Of course they're not as good as BlueRay etc, but to me and clearly many others who're okay with a bit of quality loss for a smaller file size they're more than acceptable in normal viewing (commonly 8-12 feet on a 32 inch screen?).

    I'm of course wrong on my '10mb per minute at 1080p' maths; although I've seen some 1080p movies at 1gb, they're more commonly 1.5-1.8gb - so 17/20mb per minute runtime.

    And I thought that a commercial single layer dvd held 4.7gb, comfortably accommodating a 2-hour movie and so requiring about 2gb per hour runtime - a file size of 33mb per minute (same as you mention for 'downloads which look good') and probably encoded with MPEG 2. So in view of the smaller file sizes of h.264 I'd have thought 20mb per minute to be ok.

    With my home movies, I don't want perfection - just something with a good quality to size ratio, practical for storage and distribution (burn it to a data disc so it can be handed/sent to a friend/relative).

    Although I don't want to get into the whole 'you can't see the difference between 720/1080 unless you're three foot away from a mile-wide screen' thing, I'd probably reduce 'em to 720p anyway.

    But, sticking with 1080...

    Footage originates from a Panasonic cam - my wife does it so I don't know the details but they arrive on the Mac as 12Mbps .mts files.

    New to this, she's been saving from Final Cut as .mov with a ProRes codec - hence the example of 30gb for 30 minutes runtime.

    Trying to help, I'm aware of 'oh, use 264 - save as .mp4 for compatability' and that's about where my knowledge ends and my playing with bit rates begins.

    And, my only guide is either commercial dvds and downloaded movies - with the latter clearly lower quality than the former but still acceptable.

    In test converts I've used MPEG Streamclip because as you say it's clearly faster than either Final Cut or QT Pro (which I think FC uses).

    From memory, Handbrake seems similar performance to MPEG Streamclip, which both by default deliver at approx 8-10Mbps and 2-2.5gb filesize for that 30-minute example and clearly more practical for what appears to be minimal degradation. But that still seems high at 80mb per minute so some more experimenting is required.

    (By comparison, in default settings, Adobe Media Exporter saved that as an 8gb file with a 30Mbps rate - which seems needlessly high, and didin't appear to look much better than the above examples.)

    Having read more about it, I can accept that I'll not get rates a slow as the downlaoded items, because it's likely that such small sizes are achieved by using filters and settings which significantly help compression and reduce file size while making the film still seem high quality, but which also increase the encode time to impractical levels.
  8. macrumors 6502a

    Mar 6, 2007
    From what I've seen, Hollywood movies are typically around 50MB per minute. Assuming H.264 to be twice as efficient as MPEG-2, the equivalent 1080p bit rate would be around 12Mb/s.

    But high contrast Hollywood lighting will hold up better than a lot of typical home movie lighting when compressed aggressively.

    Try setting a target bit rate of 6,000Kb/s and see if you find the image quality acceptable.
  9. thread starter macrumors member

    Jan 22, 2008
  10. macrumors regular

    Dec 11, 2012
    What you don't understand is the difference between codecs. DVD uses an mpeg2 codec, and the max bit rate per DVD spec is around 9 Mbps/s, that included audio.

    Yes a standard DVD is a single side, single layer 4.7 gb capacity, but most movie pressed DVDs are actually dual layer, so they can max out the quality.

    Keep in mind you are comparing apples to oranges, as DVD spec is only 720x480.. And the mpeg2 codec is of a different beast then h.264, mp4, cine pack, prores, etc.

    Your best bet as i mentioned is to throttle the bit rate around 6-8 Mbps/s, OR just do a test and dont throttle it, and let the software chow through it and see how large ur files are.

    Also, look for any presences when compressing that mentions 2 pass.. This lengthens encode time but yields better quality, usually at a smaller size.
  11. thread starter macrumors member

    Jan 22, 2008

    I understand that h264 should get similar quality to mpeg2, but at probably around 50-70% of the file size.

    And dual layer pressed discs are relative recent - there's plenty of singles, and it's on that which I did my calcs.

    I hadn't realized that dvds were only 720.

    That 6-8 Mbps/s should be ok - ok, so it's still a gig and a bit for a half-hour runtime, but I can live with that.
  12. macrumors 6502

    Apr 23, 2010
    Just so there's no confusion, the 720 referred to in DVDs is 720x480 (720 pixels across by 480 pixels high), while the 720 that is associated with HD is 1280 x 720). The latter has ~2.5 times more pixels. Also, consider that HD offers more pixel depth (more colors) which contributes to picture quality. This gets complicated very quickly. Which is why Chad3Eleven's advice is good: Picture a number that should work, and adjust from there. The work is very CPU intensive and can take a long time. Try a few 2-3 minutes snips first to see how they go: soccer/softball games, day at the beach, holiday dinner, backyard birthday party.
  13. thread starter macrumors member

    Jan 22, 2008

    Yes, I'd realised the numbers-thing a while ago - having gotten initially confused with '720'.

    I'm now appreciating that encoding can be very variable, and that experimenting can be valuable.

    And, as this thread now seems to be petering out, thanks again from me to all who've taken the time and made the effort to help. It's genuinely appreciated.
  14. macrumors 6502a

    Mar 6, 2007
    This isn't true. All consumer SD and HD video is 8-bit (16 million colours).
  15. macrumors regular

    Dec 11, 2012
  16. macrumors 6502

    Apr 23, 2010
    I stand corrected -- sorry for any misinformation. And here I thought saw better color when viewing HD compared to DVD.
  17. macrumors 6502a

    Parkin Pig

    I compress my files with Handbrake, which is considerably faster than exporting via Quicktime. I always save in 720p (1280x720) as my TV is 40" and I can barely tell the difference. After much testing I found 3200kbps gives a reliably crisp picture across high and low exposure whilst producing what I feel are acceptable file sizes. Scaled up to 1080p this would be 7200kbps, although this is an approximation as the soundtrack will not be scaled up.
  18. thread starter macrumors member

    Jan 22, 2008
    Thanks. The 'barely tell the difference' point is interesting - something I've read elsewhere.

    I looked at some 1080 downloads today,and although when viewing at monitor distance I can see they're better quality than 720, from more than a few feet away they appear similar.
  19. macrumors regular

    Dec 11, 2012
    I never said to use quicktime, I said to create a Quicktime. I mentioned using streamclip to the OP as the interface is a smidge less cramped then using Handbrake.

    Not sure what you meant by 1080p seems smaller? Keep in mind these are pixel sizes.. so 1080 files can have 1920x1080 dimensions, yet many films are shot at a 21x9 ratio, which yields 1920x800 size... But to your point, it depends on the resolution of your monitor. If it is 1920x1080, and you watch a 720p film at full screen it will look soft (because it is stretched) but if you watch a 1080p movie full screen, it will retain its native size at a 1:1 size with the display.

    Theres a chance that when you search for movies online, and they are listed as "1080p", they actually could be smaller.. (I've seen 1080p in the file name, and they really are just DVD rips, 720x480) To get the actual size of the movie file you have to open it up in a program, like quicktime, VLC player, etc, and get the info on them.

    Also, dual layer DVDs are not new.. they've been around since the inception of DVDs. I took a DVD course in college 13 years ago and learned the different types of DVDs, DVD-9 being single sided, dual layer.

  20. macrumors 6502a

    Parkin Pig

    Sorry - crossed wires there - the OP mentioned Quicktime - I just quoted your suggested bit rate as it coincided with the settings I settled on after much experimentation.
  21. macrumors regular

    Dec 12, 2005
    might be worth looking at a blu ray drive(, or even DL-DVD's.)

    if your recording at 1080p (your not up-scaling are you?) then blu ray may be the ideal for you, both easy TV playback and computer playback to.
  22. thread starter macrumors member

    Jan 22, 2008

    Personally, with the way we view things, I'm happy to avoid 1080 and stick with 720.
  23. macrumors regular

    Dec 12, 2005
    i have a lot of home video shot on my camera scattered over a bunch of HD's, it's a pain to pull things out so i keep some dvd's around near the TV to play home videos when i want them.

    there's still something nice about just pulling out a disc and puting it on without having to mess with which external drive and which folder etc..

    only mentioned blu ray as your talking HD size, im happy to have my edits at dvd quality for home viewing.
    (but i do keep the original un-edited video to if i can)

    just do what your & your partner are happiest with.

    if i send some video to family i do it on a dvd as people have 99% of the time no problems playing it.

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