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Re: H264 and quicktime 7

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  • Steve Watkins
    Thanks for the samples. OK well I see your tests as being extremely promising for h.264. If I am thinking correctly Your h.264 example is handling 8 times more
    Message 1 of 13 , May 1 8:18 AM
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      Thanks for the samples.

      OK well I see your tests as being extremely promising for h.264.

      If I am thinking correctly Your h.264 example is handling 8 times more information than
      the 3ivx sample:

      Your 3ivx is at 320x240 wheras the h.264 at 640x480 has 4 times as many pixels. And
      the framerate on your H.264 clip is 30fps as opposed to 15fps in the 3ivx example. So
      thats 8 times as much raw video being handled in the h.264 clip, but the filesize is only
      twice as big as the 3ivx.

      have I got that right?

      The quality of your h.264 clip is somewhat spoiled by interlacing issues. I can see the
      dreaded jaggedy lines at various points.

      Anyway I now own a Mac mini, hoorah, got tiger on it and just bought quicktime 7 pro 10
      minutes ago, so I will see what tests I can do to help evaluate h.264 further.

      The main problem so far is that I have not seen clips in 3ivx and h.264 that can be directly
      compared due to people picking different resolutions etc.

      Jason Romney, cheers for the H.264 clip yopu have done too. Its in 3gp format at
      resolutions designed for mobile phones, so it doesnt look very nice on my computer.

      Cheers

      Steve of Elbows

      --- In videoblogging@yahoogroups.com, Josh Wolf <inthecity@s...> wrote:
      > Jan, you're not missing much -- but, since you asked -- I'm putting
      > up a 3ivx version right now...
      >
      > Josh
      >
      > http://thisrevolution.blogspot.com
      >
      >
      > On May 1, 2005, at 1:18 AM, Jan McLaughlin wrote:
      >
      > > Josh,
      > >
      > > My G4 QT6 Pro came back with a "QT doesn't have the software" error
      > > when accessing the vid page.
      > >
      > > Jan
      > > [growling like a Tiger]
      > >
      > > On May 1, 2005, at 1:40 AM, Josh Wolf wrote:
      > >
      > > > I've got some video from the Tiger Launch at the SF Apple store in
      > > > H264 on my blog. I put it up at 640x480 in the hopes that I could
      > > > make a file that's manageable, and yet looks good for full-screen
      > > > video. No luck... oh well... I think I agree with Michael that 3IVX
      > > > seems to be just as good as H264 for the most part. It certainly is
      > > > more intuitive when it comes to tweaking the preferences for the
      > > codec.
      > > >
      > > > Here's the clip from the launch:
      > > > http://tinyurl.com/de3ku
      > > >
      > > > Josh
      > > >
      > > > On Apr 30, 2005, at 9:38 PM, Jason Romney wrote:
      > > >
      > > >> Hi Folks,
      > > >>
      > > >> I've uploaded to www.netvideo.com.au an H264 edition of the
      > > >> Netvideo episode
      > > >> which is about Tiger, having encoded it on the Tiger I've installed
      > > >> (following an upgrade to Quicktime 7).
      > > >>
      > > >> http://homepage.mac.com/jason_romney/JasonSwifte290405.3gp
      > > >>
      > > >> I'm having a lot of trouble getting the framerate right in H263
      > > >> encodes, by
      > > >> the way, and would appreciate anyone's insights here. H264 works
      > > >> fine when I
      > > >> play it back, but H263 seems to only show the first frames of the
      > > >> video and
      > > >> then somehow get "stuck" on a frame and refuse to show the rest
      > > of the
      > > >> video. The audio is fine. Does anyone have some H263 video encode
      > > >> configuration settings that work well for them? And on which
      > > >> cellphones have
      > > >> people tested H263, and of course, also, H264 encodes, for good
      > > smooth
      > > >> playback so far?
      > > >>
      > > >> By the way, overall, I'm delighted with Tiger, but I've had to
      > > update
      > > >> numerous pieces of software at considerable expense (eg Timbuktu
      > > >> Pro). In
      > > >> addition, some critical software I use often, such as
      > > >> BlogWaveStudio (which
      > > >> I use to publish my Web site), quits in Tiger and a new version
      > > >> 1.9.1 isn't
      > > >> expected for a week or two...so its back to manual coding for a
      > > while.
      > > >>
      > > >> Kind regards,
      > > >> Jason Romney
      > > >>
      > > >>
      > > >>
      > > >>
      > > >>
      > > >> Yahoo! Groups Links
      > > >> To visit your group on the web, go to:
      > > >> http://groups.yahoo.com/group/videoblogging/
      > > >>
      > > >> To unsubscribe from this group, send an email to:
      > > >> videoblogging-unsubscribe@yahoogroups.com
      > > >>
      > > >> Your use of Yahoo! Groups is subject to the Yahoo! Terms of
      > > Service.
      > > >>
      > > >
      > > >
      > > > ____________________________________________
      > > > "Don't hate the media, become the media."- Jello Biafra
      > > >
      > > >
      > > >
      > > >
      > > > Yahoo! Groups Links
      > > >
      > > >
      > > >
      > > >
      > > >
      > > >
      > > >
      > >
      > >
      > > Yahoo! Groups Links
      > > To visit your group on the web, go to:
      > > http://groups.yahoo.com/group/videoblogging/
      > >
      > > To unsubscribe from this group, send an email to:
      > > videoblogging-unsubscribe@yahoogroups.com
      > >
      > > Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
      > >
      >
      >
      > ____________________________________________
      > "Don't hate the media, become the media."- Jello Biafra
    • Michael Verdi
      ... Hey Steve, Actually, doubling the framerate doesn t double the file size. In fact it only produces a slight increase. This is something that seems very
      Message 2 of 13 , May 1 10:11 AM
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        On May 1, 2005, at 11:18 AM, Steve Watkins wrote:

        > Thanks for the samples.
        >
        > OK well I see your tests as being extremely promising for h.264.
        >
        > If I am thinking correctly Your h.264 example is handling 8 times
        > more information than
        > the 3ivx sample:
        >
        > Your 3ivx is at 320x240 wheras the h.264 at 640x480 has 4 times as
        > many pixels. And
        > the framerate on your H.264 clip is 30fps as opposed to 15fps in
        > the 3ivx example. So
        > thats 8 times as much raw video being handled in the h.264 clip,
        > but the filesize is only
        > twice as big as the 3ivx.
        >
        > have I got that right?
        >

        Hey Steve,
        Actually, doubling the framerate doesn't double the file size. In
        fact it only produces a slight increase. This is something that
        seems very counter intuitive but I've run across it before. I have
        no idea why this is. Does anybody out there know?
        Thanks,

        -Verdi
        http://michaelverdi.com
        http://freevlog.blogspot.com
      • Steve Watkins
        Yes its because of the way many forms of compression works. They record complete frames of video only occasionally (keyframes) and other frames are stored
        Message 3 of 13 , May 1 11:03 AM
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          Yes its because of the way many forms of compression works. They record complete
          frames of video only occasionally (keyframes) and other frames are stored like ' what has
          changed since the last frame' rather than the entire frame being stored.

          If you tell the encoder to make video of a certain datarate, it cant go above that no matter
          what framerate and resolution you use, so the file wont be any larger, just more
          compressed and more ugly.

          When I was talking about 4 and 8 times more information, I was talking about
          uncompressed video, how much 'raw information' the video encoder has to squeeze into
          whatever datarate you have specified.

          So returnign to the tiger store opening video as an example:

          The datarate for the 3ivx version is 258kbits/sec

          The datarate for the h264 version has beeen set to around 658kbits/sec

          These numbers probably include the audio too, but I wont worry about that for now.

          So the h.264 codec has been given just over twice as many bits per second in which to
          store the video. But it is being told to store the video with 4 times as many pixels and
          twice the number of frames = 8 times more raw video information in just over twice as
          much space.

          Anyway the words Ive used to explain this has probably made my explanation not 100%
          technically accurate, but hopefully its of some use.

          A starting point for testing how good h.264 really is would be to encode with exactly the
          same framerate, datarate, keyframe settings, resolution and audio settings as you already
          use in 3ivx. Does it look better than 3ivx then?

          More from me later once Ive actually managed to do testing on my mac.

          Cheers

          Steve of Elbows

          --- In videoblogging@yahoogroups.com, Michael Verdi <michael@m...> wrote:
          > Hey Steve,
          > Actually, doubling the framerate doesn't double the file size. In
          > fact it only produces a slight increase. This is something that
          > seems very counter intuitive but I've run across it before. I have
          > no idea why this is. Does anybody out there know?
          > Thanks,
          >
          > -Verdi
          > http://michaelverdi.com
          > http://freevlog.blogspot.com
        • Adrian Miles
          around the 1/5/05 Michael Verdi mentioned about Re: [videoblogging] ... 1. frame rate can affect file size but it is not symmetrical (double fps doesn t =
          Message 4 of 13 , May 4 6:19 PM
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            around the 1/5/05 Michael Verdi mentioned about Re: [videoblogging]
            Re: H264 and quicktime 7 that:
            >Actually, doubling the framerate doesn't double the file size. In
            >fact it only produces a slight increase. This is something that
            >seems very counter intuitive but I've run across it before. I have
            >no idea why this is. Does anybody out there know?

            1. frame rate can affect file size but it is not symmetrical (double
            fps doesn't = double size). This is due to delta frames, key frames
            and frame differencing.

            2. this is *basic* compression.

            3. A good modern codec (eg H.264) should be allowed to auto insert
            keyframes. If you override this you're going to produce stoopid sizes.

            4. a key frame is the codec saying, hey, I need to remember *all* the
            info for this frame, because it is so different from the last one.
            Then the codec only remembers what is different from that key frame
            for the next n frames. Until *it* decides it needs a new keyframe.
            (this is why you let it decide.) Very good codecs do this forwards
            and backwards (so how different from last keyframe, how different
            from next keyframe).

            5. this is why very good codecs do 2 passes, they have to analyse all
            this first.

            6. if you film yourself not moving, against a still background, you
            can compress down to about 1 kbit a second and it will look great
            (I'm serious). If you jump around all over the place then more
            keyframes are needed, there is much more differencing, file size is
            bigger.

            7. However, frame size makes a big difference. double frame size (say
            160 x 120 to 320 x 240) and you quadruple the amount of data required.

            8. However, dropping frame rate can also help since it doesn't have
            to draw so much, and you get less key frames (potentially).

            9. Never increase the frame rate in compression.

            10. Compression is lossy, it throws data away. If you try to add data
            then you are asking the codec to invent data it doesn't have. It
            would be like compressing to jpeg in photoshop, then converting it to
            32bit RGB, and complaining about the crappy quality of your eps
            artwork. :-)

            11. Never increase the frame size in compression.

            12. Never increase anything in compression.

            13. If you manually set keyframes (say every 5 seconds), and you've
            got 10 seconds of a vase, then you've added a pile of data that is
            100% irrelevant and unneeded.

            14. If you are serving off RTSP (real time) then you do manually
            insert keyframes. Videbloggers don't use rtsp, we use http (for very
            good reasons).
            --
            cheers
            Adrian Miles
            ____________
            hypertext.RMIT
            http://hypertext.rmit.edu.au/vlog
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