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26th October 2005, 16:27 | #1 | Link |
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WMV9 bidirectional frames performance
I've been playing around with several WMV encoders (including one from MS), and it seems like this standard exhibits low performance concerning B-frames.
While MPEG4's use of B frames usually reduce bitstream size by 10-20% (in relation to P-only streams), the WMV standard rarely shows any reduction at all (!). The encoders I checked supported 1-7 consecutive B frames, 4MV, AC prediction, and all the knacks and gadgets available in the standard. It simply seems like WMV B frames are not cheap enough, while distancing the P-vops from one another demands a large amount of bits... Can anyone comment on this? I'd like to know if this phenomenon is familiar, or am I doing something wrong? NK. |
26th October 2005, 17:50 | #3 | Link |
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Used a microsoft encoder, amongst others.
This issue has appeared across several encoders, which leads me to think it is not encoder related. My feeling is that there seems to be inherent issues with the Bidirectional frame in the wmv standard. MPEG4 uses 1 bit for SKIPed macroblocks in P frames, and 0 bits for NOT_CODED macroblocks in B frames. This results in bit reduction when presenting the B frame feature into quiet scenes. WMV uses 1 bit for SKIP in P frames, and 2 (!) bits for DIRECT SKIP in B frames. NK |
26th October 2005, 18:47 | #4 | Link |
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Join Date: Sep 2002
Posts: 139
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Interesting
It would be interesting to know whether this is really a format limitation or encoder limitation. Also, I had no idea there are third party WMV9 encoders, front-ends - sure. If you could say which you've used I'd be interested in testing them myself. |
26th October 2005, 20:04 | #5 | Link |
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what other encoders? afaik m$ is the only one providing a vc-1 codec atm
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Between the weak and the strong one it is the freedom which oppresses and the law that liberates (Jean Jacques Rousseau) I know, that I know nothing (Socrates) MPEG-4 ASP FAQ | AVC/H.264 FAQ | AAC FAQ | MP4 FAQ | MP4Menu stores DVD Menus in MP4 (guide) Ogg Theora | Ogg Vorbis use WM9 today and get Micro$oft controlling the A/V market tomorrow for free |
26th October 2005, 22:26 | #6 | Link | |
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Quote:
http://www.inlethd.com/products/fathom.htm I think it costs about $25,000! Supposedly the quality of this software/hardware-assisted solution is much better than the "stock" encoder provided by Microsoft, and you can encode HD video in real-time. |
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26th October 2005, 22:51 | #7 | Link |
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i assume these are all the same implementations: the one from m$
__________________
Between the weak and the strong one it is the freedom which oppresses and the law that liberates (Jean Jacques Rousseau) I know, that I know nothing (Socrates) MPEG-4 ASP FAQ | AVC/H.264 FAQ | AAC FAQ | MP4 FAQ | MP4Menu stores DVD Menus in MP4 (guide) Ogg Theora | Ogg Vorbis use WM9 today and get Micro$oft controlling the A/V market tomorrow for free |
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