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Thread Subject:
What is fastest video format for mmreader?

Subject: What is fastest video format for mmreader?

From: Pat Finder

Date: 4 Nov, 2009 14:42:03

Message: 1 of 2

Does anyone have any experimental evidence which video format is fastest to read in?

I'm using mmreader( ) on OsX, and this call is by far the slowest call in my program -- two or three orders of magnitude slower than the rest of the processing I'm doing.

What is the fastest compression format to decompress?
I am currently using *.mov files, but they are wrappers for other compression schemes under the covers. I could re-compress off-line if necessary. Is it fastest to read in MP4 files or Motion JPEG files, or what? Does anyone have any data on this?

Does 2009b use hardware acceleration?
I am using 2009a, and I speculate that mmreader( ) is doing all the decompression in software, even though there is a handy-dandy NVidea card installed.

What's the best batch size?
I have managed to speed it up a bit by reading in batches of 32 or 64 frames. However, the best batch size would be to read in a multiple of key-frames,
so that the each batch starts on a key frame. Is there a hidden call to get the number of frames between key frames? (Perhaps even outside of Matlab?)

Subject: What is fastest video format for mmreader?

From: Pat Finder

Date: 8 Nov, 2009 01:35:06

Message: 2 of 2

"Pat Finder" <pfinder@netacc.net> wrote in message <hcs3rr$bpf$1@fred.mathworks.com>...
> Does anyone have any experimental evidence which video format is fastest to read in?
>
> I'm using mmreader( ) on OsX, and this call is by far the slowest call in my program -- two or three orders of magnitude slower than the rest of the processing I'm doing.
>
> What is the fastest compression format to decompress?
> I am currently using *.mov files, but they are wrappers for other compression schemes under the covers. I could re-compress off-line if necessary. Is it fastest to read in MP4 files or Motion JPEG files, or what? Does anyone have any data on this?

Stumped you all eh? I'm surprised.

There ought to be a prize for raising an issue that isn't commonly known...
- Pat

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