H.264 for iPad, problems in CS5 - OK in CS3 (Mac)

Question

Hi all,
I have a CS3 project built on a PC, I've just brought into CS5 on a Mac. The encoding setup is for iPad, running full screen: H.264, 25fps, 1024x768, with a keyframe every 5 frames. I'm using the same setting as the CS3 project.
All movies out of CS3 are reported by Quicktime to be 25fps. However movies out of CS5 are reported to be 25.33fps. In addition the results look blurry and generally poor compared to CS3 for the same file size. Anyone have any advice or experiencing similar issues?
Mostly I need to ensure it comes out at 25fps as the engine/code base require 25fps with a key frame every 5 frames for movies to work correctly in App (as it has been doing with CS3 exports).

Answer 1

Whoops--yes, QT 7 is what I meant but not what I said!
(all the listings here are for the same movie)
QT X reports - 25.35 FPS (playing FPS not listed)
QT 7 reports - 25.07 FPS (playing FPS: 25)
Premiere reports - 25 FPS
Would you say this means I am actually getting 25fps?
Without having much scientific evidence to go on, I would have to say "yes." Since software playback is not strictly timed the way, say, a professional video tape playback would be, there is bound to be some variability in how that file actually gets played back. It will vary based on the host computer, the file, and the player used. Ultimately, though, it's the way the file is encoded that matters, and I believe that the file actually is 25fps as you've specified.
The most important question is: have you tried one of these CS5 exports in your destination application to see if everything works correctly? If they do, I don't think you have to worry about too much more; after all, based on your description, the most important factor is that you have keyframes encoded into the video stream for navigation/cueing. If this works, the playback framerate should be largely irrelevant, at least in how it is reported in a host of different playback applications.
I am still wondering about the Data Rate, appearing (in QT) to be below the range listed in the Encoder settings.Using variable between 4 - 8Mbps yet the output is reported as:
QT 7 - 3837.74 kbits/s
Premiere is says Average Data Rate: 463 KB / second
Changing to CBR with 5 Mb/s
QT 7 reports - 25.07 FPS (playing FPS: 25) - 4128.64 kbits/s
Premiere reports - 25 FPD - Average Data Rate: 498 KB / second
There is bound to be some variation between the data rates of two files encoded even with the same encoding parameters, particularly when you're using VBR (variable bit rate) encoding. The amount of used bits will vary throughout the course of an encoded video stream, as some portions will require more bits to encode cleanly, while others can be compressed much more efficiently and therefore use fewer available bits. A busier video will require more of the available bits than one with less action. This would account for variations in data rate between two files using the same encoding settings.
Now, if you are talking about the difference between what QT7 and Premiere report as far as data rate is concerned--that's simply a reporting issue. QT7 is using kbits/s, or "kilobits per second," whereas Premiere is being far less precise with kBps, or "kilobytes per second." One kilobyte per second (1 kBps) is roughly equal to eight kilobits per second (8 kbps), so if you multiply one the Premiere-reported data rates by 8, you get the QT7 rate.
For example: 8 kilobits x 463 kBps = 3704 kbps; fairly similar to what QT7 reported.
Why the difference? Well, one may be factoring in audio bitrate as well as video bitrate, or the Premiere reported data rate is less precise, or maybe just the fact that binary math is a little more involved than simple straightforward calculations In any event, they're both "right;" it just depends how accurate you need to be.
Is Premiere the best place to check for data rates and FPS? Could do with one reliable source
My recommendation would be MediaInfo; it's available for many platforms, including Mac, and gives a great deal of information about any particular file.