MJPEG to JPEG transcoder

[Guest]

Archived from groups: rec.video.desktop (More info?)

Is there a program that would allow extracting selected MJPEG
frames directly into JPEG/JFIF format, without recompressing?
My understanding is that it should be technically possible
to copy the raw frame data as such (with no modifications)
inside a JFIF wrapper.

Conventional video editors allow extracting single frames,
but they decompress the MJPEG data and then recompress it
again into a JPEG file.

--
znark

 

[Guest]

Archived from groups: rec.video.desktop (More info?)

On Thu, 1 Apr 2004 01:11:03 +0300, "Jukka Aho" <jukka.aho@iki.fi>
wrote:

>Is there a program that would allow extracting selected MJPEG
>frames directly into JPEG/JFIF format, without recompressing?
>My understanding is that it should be technically possible
>to copy the raw frame data as such (with no modifications)
>inside a JFIF wrapper.

It should be possible, and it should be easy. AVI files are structured
basically as a header, then interleaved chunks of video and audio. At
the beginning of each chunk, its size is indicated, thus telling you
where the next chunk begins. All you would need is copying the bytes
in a video chunk to a jpeg image. This should not take a programmer
more than a spare time. (Me? Have not programmed in months, and hardly
can find a spare time! But who knows, may be one day...)