Sagittaire
9th August 2006, 13:55
I have an enthralling debate on HDTV forum. If there are codec developper in the place what do you think about that ... ???
720p will never be a sound compromise for any of us, as 1080i is way better when done properly.
Why settle for cheap sparkling wine when you can get good champagne?
I say that with unlimited bitrate and with movie source, 1080p will be always better than 1080i and 1080i always better than 720p. If you use very high bitrate 1080i will be better way than 720p, but if you use less an less bitrate 720p will be better way, with less an less bitrate best way become 576p ... etc etc etc
And problem is that actual HDTV don't use unlimited bitrate. Actual US HDTV use medium bitrate (average 8 - 20 Mbps) for MPEG2 at 1080i and result is not always perfect and by far. With same bitrate 720p could be very better way for very uncompressible source for example. Best quality is not higher resolution, best quality is always better compromise between bitrate/resolution.
720p as a broadcast format is always 720p @ 60 fps. So this means that the stream is actually encoded at that rate as well, with redundant frames at least in case of film-based contents.
1080i (film-based contents) however is either distributed as 1080i w/telecine flags, or with hardcoded pulldown.
In case of telecine-flagged contents, only 24 frames per second are encoded in the stream.
Well HDTV it's not only movie. For real 60 fps source 720p 60 fps will be always really better than 1080i 30fps with true interlacing because:
- Progressive encoding process is always more efficient than Interlaced encoding process
- Progressive decoding process is always more efficient than Interlaced decoding process
- Interlaced field use half vertical resolution (pseudo anamorphic field) and for HVS (Human Visual System) the vertical resolution is more important for eyes. 1280*720 60 frame/sec progressive frame are simply better for eyes than anamorphic 1920*540 60 field/sec
DVD9 is maybe sufficient for about 10 percent of the movies out there when encoded straight from the masters, but your claim that DVD9 is largely sufficient in general simply shows your ignorance of the subject matter.
You have obviously never seen a master tape or a DI, so you cannot even have an idea of how much information (detail) is already lost in braodcast HD.
Well I think that (from my experience) H264 1080p for DVD9 will done something like average quantizer q15 for 120 min medium compressibility source. It's a very high quality level for 1080p source. Potentialy a very better quality than Quick Time 1080p HD H264 trailers.
http://www.apple.com/trailers/
As for your claim of h.264 being better than AVC at mid to low bitrates: show me recent quotes by VC-1 developers that say so.
You won't find any, neither do you have access to the current implementation of VC-1.
Well Zambelli say that about curent VC-1 implementation: "This is a very good point. VC-1 was designed to be a less complex codec than H.264, thus requiring less decoding resources. Any advantage you gain in encoding efficiency with H.264 over VC-1 - you're going to have to pay for it on the decoding side. (CABAC, for example.)"
http://forum.doom9.org/showthread.php?p=813716#post813716
Regarding your claim that 45 GByte should be sufficient for lossless encoding:
A recent extensive comparison of lossless encoders (with raw source material) showed that YUV12 is approx 10 percent more effective than YV12.
Also neither of them were able to gain compression ratios of more than 4.4:1
Now, lets assume a raw uncompressed 4:4:4 (4:2:0 is not desirable in that case, as you could hardly call it true raw uncompressed) datarate for 720p24 (not 720p60) of roughly 640 Mbps.
A 4.4:1 compression ratio would thus reduce that rate to 145 Mbps.
This would mean that the max duration on a 45,000,000,000 byte disc is less than 2500 seconds (still impressive, but quite a distance from your claim).
The figure for 4:2:0 720p24 would be 332 Mbps, and for 4:2:0 720p60 it would be 818 Mbps.
Btw, back in early 2004 the best compression ratios for lossless YUV12 were 3.3:1 (YV12 was 3:1). So it took them 2.5 years to improve that ratio to 4.4:1
To fit a 2 hour movie on a 45 GByte disc they would have to increase that ratio to approx. 12.8:1
Well I make very simple test with high quality full 16/9 720p YV12 source:
- uncompressed 720p YV12 encoding done 260 Mbps
- FFV1 YV12 lossless encoding done 52 Mbps and 1:5 ratio
- 120 min for 45 GB Blu Ray disk done 50 Mbps
An another test here
http://forum.doom9.org/showthread.php?t=90031
Conclusion: I think that it's possible to make YV12 720p lossless encoding for 45 GB BR in the majority of the cases because movie are generaly really compressible (2.35 aspect and real 1280*544 image, good spatio-temporel compressibility for movie)
720p will never be a sound compromise for any of us, as 1080i is way better when done properly.
Why settle for cheap sparkling wine when you can get good champagne?
I say that with unlimited bitrate and with movie source, 1080p will be always better than 1080i and 1080i always better than 720p. If you use very high bitrate 1080i will be better way than 720p, but if you use less an less bitrate 720p will be better way, with less an less bitrate best way become 576p ... etc etc etc
And problem is that actual HDTV don't use unlimited bitrate. Actual US HDTV use medium bitrate (average 8 - 20 Mbps) for MPEG2 at 1080i and result is not always perfect and by far. With same bitrate 720p could be very better way for very uncompressible source for example. Best quality is not higher resolution, best quality is always better compromise between bitrate/resolution.
720p as a broadcast format is always 720p @ 60 fps. So this means that the stream is actually encoded at that rate as well, with redundant frames at least in case of film-based contents.
1080i (film-based contents) however is either distributed as 1080i w/telecine flags, or with hardcoded pulldown.
In case of telecine-flagged contents, only 24 frames per second are encoded in the stream.
Well HDTV it's not only movie. For real 60 fps source 720p 60 fps will be always really better than 1080i 30fps with true interlacing because:
- Progressive encoding process is always more efficient than Interlaced encoding process
- Progressive decoding process is always more efficient than Interlaced decoding process
- Interlaced field use half vertical resolution (pseudo anamorphic field) and for HVS (Human Visual System) the vertical resolution is more important for eyes. 1280*720 60 frame/sec progressive frame are simply better for eyes than anamorphic 1920*540 60 field/sec
DVD9 is maybe sufficient for about 10 percent of the movies out there when encoded straight from the masters, but your claim that DVD9 is largely sufficient in general simply shows your ignorance of the subject matter.
You have obviously never seen a master tape or a DI, so you cannot even have an idea of how much information (detail) is already lost in braodcast HD.
Well I think that (from my experience) H264 1080p for DVD9 will done something like average quantizer q15 for 120 min medium compressibility source. It's a very high quality level for 1080p source. Potentialy a very better quality than Quick Time 1080p HD H264 trailers.
http://www.apple.com/trailers/
As for your claim of h.264 being better than AVC at mid to low bitrates: show me recent quotes by VC-1 developers that say so.
You won't find any, neither do you have access to the current implementation of VC-1.
Well Zambelli say that about curent VC-1 implementation: "This is a very good point. VC-1 was designed to be a less complex codec than H.264, thus requiring less decoding resources. Any advantage you gain in encoding efficiency with H.264 over VC-1 - you're going to have to pay for it on the decoding side. (CABAC, for example.)"
http://forum.doom9.org/showthread.php?p=813716#post813716
Regarding your claim that 45 GByte should be sufficient for lossless encoding:
A recent extensive comparison of lossless encoders (with raw source material) showed that YUV12 is approx 10 percent more effective than YV12.
Also neither of them were able to gain compression ratios of more than 4.4:1
Now, lets assume a raw uncompressed 4:4:4 (4:2:0 is not desirable in that case, as you could hardly call it true raw uncompressed) datarate for 720p24 (not 720p60) of roughly 640 Mbps.
A 4.4:1 compression ratio would thus reduce that rate to 145 Mbps.
This would mean that the max duration on a 45,000,000,000 byte disc is less than 2500 seconds (still impressive, but quite a distance from your claim).
The figure for 4:2:0 720p24 would be 332 Mbps, and for 4:2:0 720p60 it would be 818 Mbps.
Btw, back in early 2004 the best compression ratios for lossless YUV12 were 3.3:1 (YV12 was 3:1). So it took them 2.5 years to improve that ratio to 4.4:1
To fit a 2 hour movie on a 45 GByte disc they would have to increase that ratio to approx. 12.8:1
Well I make very simple test with high quality full 16/9 720p YV12 source:
- uncompressed 720p YV12 encoding done 260 Mbps
- FFV1 YV12 lossless encoding done 52 Mbps and 1:5 ratio
- 120 min for 45 GB Blu Ray disk done 50 Mbps
An another test here
http://forum.doom9.org/showthread.php?t=90031
Conclusion: I think that it's possible to make YV12 720p lossless encoding for 45 GB BR in the majority of the cases because movie are generaly really compressible (2.35 aspect and real 1280*544 image, good spatio-temporel compressibility for movie)