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Re: Compressing videos for iPhone 4 - Best quality?

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James Bayliss-Smith
Re: Compressing videos for iPhone 4 - Best quality?
on Aug 24, 2010 at 1:26:05 am

Thanks for the link, I can see that it is a very useful programme although not upadated for the iPhone 4 yet. So I put through my two test videos and everything is the same except for the bit rate

- Bitrate: Max.: Undefined
Average: 15.4 Mbps
Min.: Undefined
- Bitrate: Max.: Undefined
Average: 1 475 Kbps
Min.: Undefined

So I guess 15.4 Mbps is above the "Threshold". Is that what you mean by threshold, the bitrate threshold?

If I cut and paste the specs again from the Apple website and ignore the audio for a moment

Video formats supported [by iPhone 4]:

H.264 video up to 720p, 30 frames per second, Main Profile level 3.1 .m4v, .mp4, and .mov file formats;

MPEG-4 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Simple Profile .m4v, .mp4, and .mov file formats;

Motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 720 pixels, 30 frames per second, .avi file format

Does this mean I will achieve better quality with motion Jpeg as I can go up to 35 Mbps?

What is the threshhold for h.264, MPEG 4 is clearly stated as 2.5 Mbs but the H.264 only says up to 720p. What do you think this means?

What is the profile level? What does this mean?

What do you mean when you say Compressor sets the 'level' and the 'profile'? What "level" the bit rate?

Sorry for all the questions I'll do some more reading and some more tests but I'm just trying to get my head around the theory?


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