HDMI video - compression and uncompressed and bitrates

[Christopher2222]

Help me understand. Do I have this right?

My Bell satellite receiver gets a compressed video signal and uncompresses it on the fly to deliver to my TV. What compression does it use? H.264? Then, if I record the show on my PVR, it gets encrypted to a compressed format and when I play it back again it uncompresses through the HDMI to my TV. I worked it out but not sure if it's right that if my 2 Terrabyte PVR shows 500 hours of space available by the satellite receiver that means it can record shows at 8.8 megabits per second however that's if it's uncompressed? Is that right? Maybe the shows are actually compressed 20Mbps down to 8.8Mbps and get uncompressed back up to 20Mbps when replayed?

So if I capture the signal I'm capturing the uncompressed format at whatever I set my bitrate to say 5Mbps. But if the HDMI stream is actually 20Mbps I'm losing 15Mbps of data. So what that means I should do, is capture the highest rate available (for the colossus 2 that's 13Mbps) then take another step and re-author the captured video rate (2 pass of course) back down? To me it doesn't make sense to capture the source at 13Mbps and recode down to 5Mbps or just capture right away at 5Mbps. You'll end up with the same bitrates but won't the quality and the file sizes be exactly the same in the end? Seems to me the only difference is one route just takes longer than the other?

Am I completely out to lunch on that? What's wrong with my thinking?

[pandy]

Am I completely out to lunch on that? What's wrong with my thinking?

Your receiver receive some signal, this signal is compressed video with average 10Mbps bitrate, such video can be also stored on HDD (i assume your PVR is integrated with your receiver) as such you storing compressed video in original (delivery) format - 500hr's specified for recorder is approximation with assumption of some average bitrate - for videos with lower bitrate than average it will be more than 500hr's, for video with bitrate higher than average it will be less than 500hrs.

HDMI bitrate for uncompressed video is way over 1Gbps (in fact it is closer to 5Gbps - there is also HDMI lossy compression introduced not so late ago - compression is lossy but not this kind of as for H.264).

And answer for second part is more difficult - depend on content however to match quality present in your decompressed source it must be higher than bitrate of source before decompression. Nowadays decent H.264 encoder is able to deliver good quality for HD at 5 - 6Mbps.
If you can try to record originally compressed source (so noe decompression and recompression) - quality will be the same as broadcasted.