[FFmpeg-devel] H.264 CABAC Decoder on IBM Cell

Jason Garrett-Glaser darkshikari
Thu May 7 13:43:34 CEST 2009

On Thu, May 7, 2009 at 4:39 AM, Erich Marth
<destinationcloud at googlemail.com> wrote:
> Dear ffmpeg Team,
> my name is Erich Marth and I'm currently doing some research on porting
> ffmpeg or to be more preciously the h.264 codec to the cell architecture.
> Till now I do have a good code status, but i do suffer big problems in
> doing an optimized version of the cabac entropy decoder.
> F.e.: Playing Pirates III (1080p) with CAVLC, an I frame takes
> about 18ms to decode, but trying to decode a single slices I frame from
> a 720p cabac video takes about 100ms to decode.

I'm going to blame the fact that the primary core of the Cell
(stupidly) doesn't have a barrel shift unit, resulting in variable
shifts, such as those in renormalization, being implemented in
microcode (and correspondingly being extraordinarily slow).

But that's just a guess.  It needs to be profiled.

Dark Shikari

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