BDs in AVC versus MPEG and optimum bitrates

[jmkoch]

Some BD burning products offer the optiion to burn in AVC or MPEG and let one pick a bitrate as low as 5 MBPS or as high as 25 MBPS.

In principal, a higher bitrate allows for higher maximum image information transmission, which could mean higher image quality. However, what advantage is there, if any, in picking an output bitrate any higher than the ceiing of the source video? Only a few recent consumer HD videocams capture in AVCHD any higher than 17 mbps, and a lot capture at 13 mbps.

What are the average or ceiling bitrates for most commercial BD discs? How about that of the HD broadcasts on cable or satellite?

What are the virtues, flaws, or quirks of BD in AVC versus MPEG?

Do all (or perhaps only high end) BD players offer readings of a disc's video bitrate, pixel dimensions, constrast ratio, or sound to noise audio ratio?

[kpkelley]

Originally Posted by jmkoch

What are the virtues, flaws, or quirks of BD in AVC versus MPEG?

AVC is MPEG-4. Therefore in order to make any sense out of this question I must assume(i know that could be a mistake) that MPEG is referring to MPEG-2.

AVC is a more advanced compression codec than MPEG-2. What this means is that an identical piece of film or video compressed into mpeg-2 and avc at the same bitrate would result in more of the original raw data being recorverable in the avc file resulting in a higher quality picture. They can be equivalent in pq if mpeg-2 is allowed a higher bit-rate.

This is just a basic overview to give you a general idea. Since both of these compress the information in slightly different ways some things are treated slightly differently than they would be when using the other compression. Suffice it to say that AVC would perhaps be your best route, but if space is not an issue the mpeg-2 compression would most likely take less time.

[jmkoch]

Thanks, but aren't you really saying that, for a given piece of video at a given bitrate, the AVC file will simply be smaller (more compressed) than the MPEG one? Conversely, creation of the AVC file takes more time (or a heftier processor) to compress or play back, while the MPEG one is easier and faster to process, but bulkier on a disc.

Generally, should there be any video quality difference between the two, so long as the bitrate is the same, unless the AVC bears more compression noise?

PS: My understanding is that all AVC is a type of MPEG4, but that not all MPEG4 is AVC (in the sense of h.264). Would all BD's in "AVC" use some type of h.264? Which standard is more common for commercial BDs? Pinnacle Studio offers either MPEG or AVC as a BD burning option, but without any elaboration in the manual or on-line FAQ about the distinctions.

Is there a known gradient of the tradeoff between pixels, framerate, and bitrate for a given image result? For instance, is 1280x720 30p at 18 mbps better or worse than 1920x1080 30p at 13 mbps? Or is it pretty much "by guess and by golly"? Is 1280x720 30p at 4 mbps (the Vimeo on-line standard) perhaps really worse than 720x480 at 8.5 mbps?

Does anyone know the average or peak bitrates of: a) a typical commercial BD, b) most broadcast HD, or c) most cable HD? The providers themselves tend to bury the information or cloud it with hype. I also wonder whether the bitrates aren't tweaked based on one's subscription rate, the time of day, or the type of program. Re-runs of old-time TV in HD would really mean nothing more than Jackie Gleason with more image ghosts, dark shadows, and hot spot blowouts.

[kpkelley]

Originally Posted by jmkoch

Thanks, but aren't you really saying that, for a given piece of video at a given bitrate, the AVC file will simply be smaller (more compressed) than the MPEG one? Conversely, creation of the AVC file takes more time (or a heftier processor) to compress or play back, while the MPEG one is easier and faster to process, but bulkier on a disc.

Generally, should there be any video quality difference between the two, so long as the bitrate is the same, unless the AVC bears more compression noise?.

That's correct, in general terms the picture quality should be equivalent with the only difference being size, again generally.

Originally Posted by jmkoch

PS: My understanding is that all AVC is a type of MPEG4, but that not all MPEG4 is AVC (in the sense of h.264). Would all BD's in "AVC" use some type of h.264? Which standard is more common for commercial BDs? Pinnacle Studio offers either MPEG or AVC as a BD burning option, but without any elaboration in the manual or on-line FAQ about the distinctions.

Is there a known gradient of the tradeoff between pixels, framerate, and bitrate for a given image result? For instance, is 1280x720 30p at 18 mbps better or worse than 1920x1080 30p at 13 mbps? Or is it pretty much "by guess and by golly"? Is 1280x720 30p at 4 mbps (the Vimeo on-line standard) perhaps really worse than 720x480 at 8.5 mbps?.

VC-1 is also a type of MPEG4. As of right now, it appears that the majority of new releases are AVC with a few studios, mainly WB, releasing VC-1. Bitrates have more to do with motion, than resolution. For instance a static image of resolution 1920x1080 would have no bitrate because it's not changing. The more motion the higher the bitrate should be to avoid any compression artifacts. As for comparisons of resolutions at differeing bitrates, IDK, I suppose it would depend on the material. My guess would be that for the most part a higher resolution would continue to look better unless it was marred by significant compression artifacts.

Originally Posted by jmkoch

Does anyone know the average or peak bitrates of: a) a typical commercial BD, b) most broadcast HD, or c) most cable HD? The providers themselves tend to bury the information or cloud it with hype. I also wonder whether the bitrates aren't tweaked based on one's subscription rate, the time of day, or the type of program. Re-runs of old-time TV in HD would really mean nothing more than Jackie Gleason with more image ghosts, dark shadows, and hot spot blowouts.

Bitrates vary across the board depending on the studio, size of the disc, etc. I would say that the average bitrate of a new release is around 30mbps, with some peaks above 50 mbps. OTA hd broadcasts are not as heavily compressed as cable HD because they are restricted by the other channels that the cable company is trying to send at the same time. As for the specific bitrates of ota and cable hd, IDK.