Need to get large file sizes down to downloadable sizes-how?

Question

I am using Compressor 4 and have several professional videos I produced with Final Cut Studio in QuickTime/.MOV format using ProRes 442. They are all 720p and of course, all have large file sizes. I needed to convert them so they are compatible with iTunes as well as Apple devices (AppleTV, iPad/iPod/iPhone, etc). They also need to be downloadable in a reasonable time and I of course want to maintain a quality image. Several of the videos are about an hour long, some a little more.
I an unable to get most of these files to be small enough for practical download and still maintain an acceptable quality. For example:
I have one video (QuickTime rendered from FCPS) that runs 54 minutes. 1280x720, ProRess 422, Linear PCM with a Bit rate of 72.662. The best I seem to be able to get out of compressor is to use the setting options for "HD for Apple Devices (5 Mbs)" which gives me a file that's just over 2Gb. Not bad, and the quality is still very good, but the file size is just too big for people to download. I get reports of people getting estimates of 77 hours to download this one file.
I did try using the setting under Video Sharing Services / Large 540p Video Sharing just to see what it would give me, but it really wasn't that much smaller and the quality was noticeably degraded.
I'm confused as to what to do about this. I have downloaded things from iTunes before that are good quality, about an hour and their file sizes are simply bnot this big.
Can anyone give me some advice? Thank you. Grateful for anything you can offer.
MC

Answer 1

If you're not concerned with precise average bitrate, use h.264 codec, set bitrate to "automatic" and use the quality slider. Be sure to have "keyframes" on "automatic"; every 24 frames or so makes h.264 quite inefficient and is only useful for live-streaming, where you want people to be able to resynchronise as quickly as possible. Having multi-pass enabled might help, but I'm not sure what it does when using constant-quality encoding.
Do a test-encoding of a representative clip of maybe about rwo minutes or so, play with the quality slider and see how far down you can go and still be satisfied with the quality. Using "automatic" bitrate uses as many bits to encode each frame as is necessary to get the required quality, and file sizes will vary depending on the type of material. Complex textures and high motion will use more bits, still frames and slow pans will use very little.
A light chroma-channel denoising may help improve perceived quality, as may very light sharpening in case you scaled down the material.
If you're still not happy with the bitrate vs. quality tradeoff, try reducing the resolution, but generally you should get 720p down to around 2.5 to 3.0 Mbps with adequate quality.
On the other hand, If someone needs 77 hours to download 2 GB, they have another problem anyway. That sounds like a 56k modem connection. What's he doing trying to download HD content anyway?
Bernd