英文:
Is extract_mvs in ffmpeg able to extract mvs of sub-macroblocks(8x4/4x8, 4x4)?
问题
I want to get information of motion vectors(mvs) of h264 video, and I have tried to use ffmpeg's extract_mvs.c to slove this problem. However, I found that the extracted mvs' block size are 16x16, 16x8, 8x16 or 8x8, but none of them is 8x4, 4x8 or 4x4.
I wonder if there is any way to get the sub-macroblock's mvs?
I think there do exist mvs of sub-macroblocks(8x4, 4x8 or 4x4), as I can get information(use x264.exe) like this:
x264 [info]: mb I I16..4: 39.9% 24.5% 35.6%
x264 [info]: mb P I16..4: 1.9% 0.4% 0.2% P16..4: 20.1% 17.9% 28.4% 11.2% 7.2% skip:12.7%
x264 [info]: mb B I16..4: 0.0% 0.0% 0.0% B16..8: 42.3% 6.6% 1.8% direct: 2.3% skip:47.0% L0:31.8% L1:44.3% BI:24.0%
'P16..4: 20.1% 17.9% 28.4% 11.2% 7.2%' is the rate of 16x16, 16x8/8x16, 8x8, 8x4/4x8, and 4x4. But I don't know how to get mvs of sub-macroblocks(8x4, 4x8 or 4x4).
英文:
I want to get information of motion vectors(mvs) of h264 video, and I have tried to use ffmpeg's extract_mvs.c to slove this problem.
However, I found that the extracted mvs's block size are 16x16, 16x8, 8x16 or 8x8, but none of them is 8x4, 4x8 or 4x4.
I wonder if there is any way to get the sub-macroblock's mvs?
I think there do exist mvs of sub-macroblocks(8x4, 4x8 or 4x4), as I can get information(use x264.exe) like this:
x264 [info]: mb I I16..4: 39.9% 24.5% 35.6%
x264 [info]: mb P I16..4: 1.9% 0.4% 0.2% P16..4: 20.1% 17.9% 28.4% 11.2% 7.2% skip:12.7%
x264 [info]: mb B I16..4: 0.0% 0.0% 0.0% B16..8: 42.3% 6.6% 1.8% direct: 2.3% skip:47.0% L0:31.8% L1:44.3% BI:24.0%
'P16..4: 20.1% 17.9% 28.4% 11.2% 7.2%' is the rate of 16x16, 16x8/8x16, 8x8, 8x4/4x8, and 4x4.
But I don't know how to get mvs of sub-macroblocks(8x4, 4x8 or 4x4).
答案1
得分: 0
你可以告诉FFmpeg H264解码器使用-flags2 +export_mvs（在-i之前）来导出运动矢量（MVs）。这将以AV_FRAME_DATA_MOTION_VECTORS类型的帧侧数据的形式导出MVs，使用motion_vector.h中的数据结构。这些侧数据的一个示例使用者是codecview视频滤镜，它将在帧上绘制MVs。但是，你可以根据需要使用这些侧数据，它只是附加到帧本身的额外信息。头部表示支持所有块大小，而不仅仅是16x16 MBs。
[编辑] 请参见下面的评论，不幸的是，对于小于8x8的块大小，似乎无法实现。
英文:
You can tell the FFmpeg H264 decoder to export MVs using -flags2 +export_mvs (before -i). This should export MVs as frame side-data of type AV_FRAME_DATA_MOTION_VECTORS using the data structures in motion_vector.h. An example consumer of this side-data is the codecview video filter, which will draw the MVs on the frame itself. But you can do whatever you want with that side-data, it's just extra information on top of the frame itself. And the header suggests all blocksizes are supported, not just 16x16 MBs.
[edit] see comment below, it appears this is unfortunately not possible for sub8x8 block sizes.
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