![]() On higher parts of the compression curve, if you give adequate bitrate for that type of content, differences quickly become negligible "Faster" settings will propogate lower quality frames through the p-frames, b-frames, and non IDR i-frames Also you'll notice worse quality "faster" settings reflected more in b-frames because of the higher quantizer when you are in this bitrate range. If you're more inclined for fast settings, you're probably not using -b-adapt 2 (not very well multithreaded, exponentially slower with increasing max b-frames), but it's required to get the "optimal" b-frame placement.Īt lower parts of the compression curve, more b-frames are almost mandatory for maximum compression. There are too many variables involved, including specific type of content, level of compression, speed tradeoffs you're willing to make. Of course disabling B-Frames is not recommended! Nevertheless limiting the maximum number of B-Frames to less than 16 is reasonable, because most videos won't benefit from using more than ~4 consecutive B-Frames anyway! Raising the B-Frame limit higher than that would only slowdown the encoding process for no real benefit! If you set the B-Frame limit to 0 (the default), B-Frames will be disabled. So even if you allow up to 16 consecutive B-Frames, the encoder will rarely go that high. x264 will still decide how many consecutive B-Frames are actually used. That's because you only specify the upper bound for the number of consecutive B-Frames. Also note that allowing more B-Frames will never hurt the quality: You can even safely choose the maximum of 16 consecutive B-Frames. Therefore using B-Frames is highly recommended. B-Frames can significantly improve the visual quality of the video at the same file size. This way B-Frames can compress even more efficient than P-Frames. B-Frames refer to both, the previous and the following I-Frame (or P-Frame). Max Consecutive: This setting controls the maximum number of consecutive B-Frames.So, what do you guys think, is it advantageous to use more b frames or is there a point where you see the law of diminishing returns kick in and actually start to hurt final quality? Tmpg allows me to set the max b frames to 16 and the max reference frames to 9 when using QS and the same for x264 (incidentally, you can set up to 15 reference frames for certain resolutions). I usually use intel quick sync from within tmpg vmw5, primarily because it's about 3 times faster than x264 with the ultra fast preset on my i3 2100 (even if i use media coder, which in my experience uses the fastest encoder and decoder builds). when you try and seek you get corrupted images. the reason i'm converting them is because the original wmv's have weird playback issues, i.e. The sources are all vc-1 (in a wmv container), 720p, 4mb/s with wma audio and i'm converting them to h264 4mb/s with aac audio in an mp4 container. Just want to hear some opinions as to how many b frames and how many reference frames you guys think should be used before quality is degraded.
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