How to extract/obtain motion vectors from .mp4 videos in MATLAB?

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Tintumon 2018-2-23

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https://ww2.mathworks.cn/matlabcentral/answers/384361-how-to-extract-obtain-motion-vectors-from-mp4-videos-in-matlab

编辑： Tintumon 2020-7-6

Hello, Is there any code (or inbuilt function) for extracting motion vectors (frame-to-frame) from MPEG-4 (H.264 compressed videos)? For my work, the input video is a scene of people moving through streets/malls.

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Shahbaz Khan 2020-7-6

i have downloaded ffmpeg, how to use it to extract motion vectors? can you please guide. the file have several libraries and codes

Tintumon 2020-7-6

编辑：Tintumon 2020-7-6

Note: The answer is out of scope of this thread.

But, I will explain it.

1) Build the example programs (located in "doc\examples") by using the following command (run the command while you are in the source FFmpeg directory):

make examples

2) Execute the "extract_mvs" binary file, generated as a result of Step 1, to obtain the motion vectors from an h.264 compressed video (navigate to "doc\examples" or provide the absolute path while executing). Write the motion vectors to a text-file (outputFile.txt).

.\extract_mvs inputVideoName.extension > outputFile.txt

This ".txt" file can be read in MATLAB and used for further processing!

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Tintumon 2018-2-24

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https://ww2.mathworks.cn/matlabcentral/answers/384361-how-to-extract-obtain-motion-vectors-from-mp4-videos-in-matlab#answer_306841

Thanks again for a detailed answer.

In the case of "VideoReader": 1) What if I had multiple codecs? I guess the routine chooses the default done. Can we manually change the default setting? 2) Also, Will it produce motion vectors as one of its output?