[PD] Re: [GEM-dev] Codecs in Gem (again!) & ffmpeg
cgc at humboldtblvd.com
Wed Aug 31 06:37:38 CEST 2005
On Aug 30, 2005, at 10:05 PM, B. Bogart wrote:
> Thanks for the suggestions.
> I'm not sure about using a mpeg for the following reasons:
> #1. was does the interframe compression thing work, in other words how
> does it compare when seeking to a quicktime with photo-jpg codec?
You want to avoid interframe compression at all costs. In order to
grab a random frame in an interframe codec the nearest previous
keyframe must be found and all interframes between it and the
requested frame are decoded. You could get lucky and hit a keyframe
or be very unlucky and hit the frame right before one.
Interframe compression techniques are used almost exclusively for
final content distribution (web, DVD, ATSC). Acquisition and
production codec never use this with the exception of HDV (which is
> Aside: What id the different between mjpeg and photojpeg as a video
mjpeg is motion-jpeg which is for interlaced two field video. Each
field (50 or 60 per second) is a compressed with jpeg techniques.
> ffmpeg reports my sequence of jpegs as "mjpeg"...
It is mistaken if your sequence is single progressive frames, which
it almost certainly is.
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