[mythtv-commits] Ticket #1926: H.264 keyframe detection fixes

MythTV mythtv at cvs.mythtv.org
Wed Jun 7 10:48:06 UTC 2006

#1926: H.264 keyframe detection fixes
 Reporter:  mark_kendall at btinternet.com  |       Owner:  ijr
     Type:  patch                        |      Status:  new
 Priority:  minor                        |   Milestone:     
Component:  mythtv                       |     Version:     
 Severity:  medium                       |  
 This patch fixes two issues with h.264 frame detection.

 Firstly, a state change and hence frame count increment would be triggered
 for each slice in a picture. Typically this meant the frame count running
 at 6x the actual frame count. I've tightened it up to ensure state changes
 are only triggered when needed.

 Secondly, the BBC H.264 trial broadcasts do not use IDR slice types -
 which the keyframe detection relies on. I've re-worked based on the
 assumption that only an access unit containing an IDR contains a sequence
 parameter set - this seems to tie up with the standard and works for the
 streams I have.

 I now get accurate position maps for the BBC trials (dvb-s and dvb-t) and
 in conjunction with ticket:1925 should fully enable these broadcasts in

 Clearly I can't test this patch extensivley but it does also work for some
 h.264 transport streams I have from Germany (AnixeHD) and the US (KOAT 7?)
 passed in via the crcipnetworkrecorder.

Ticket URL: <http://cvs.mythtv.org/trac/ticket/1926>
MythTV <http://www.mythtv.org/>

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