play at double speed

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Patrick Truong 2016-10-5

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https://ww2.mathworks.cn/matlabcentral/answers/305848-play-at-double-speed

评论： Walter Roberson 2017-5-24

Hi,

I am taking a course at MATLAB academy. Is it possible to play the course video sessions in 2x speed?

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Behrang Sharif 2017-5-23

I actually have the same problem. It seems that readFrame function strictly follows the frame rate (read only!) of the VideoReader object and I could not even manage skipping frames for increasing the playback speed. Is there any way for MATLAB to read frames faster or skip frames in order to play at 2x or more?

Walter Roberson 2017-5-24

Behrang Sharif:

Your question is different. The original question was about watching MATLAB Academy instructional videos speeded up, which is difficult because no useful interactive control is given for that.

With regards to readFrame: it is not necessary to display every frame. It is, however, necessary to read every frame in any of the compressed video formats, as the decompression depends upon the previous frame having been decoded. For H.264 video, the decompression can also depend up future frames.

The only leeway that the compressed video formats have is that some of them offer "key frames", which are completely uncompressed; if you are jumping by a bunch of frames, you can jump to the key frame that most immediately proceeds the target frame, and decode from that key frame to the target frame.

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