[DVDnav-discuss] Strange DVD playback skip/freeze

[Tuomo Sipola]

Hello,

Summary: DVD playback freezes (or skips) on a physically OK disc. Is it 
a libdvd* problem?

I have a DVD disc, Buffy 7th season R2 disc 6, which exhibits strange 
beahavior during the first episode, "Touched". I have tested with two 
different discs from different boxes. I have also checked the disc with 
dvdisaster, so it is not a physical problem. The same problem occurs 
with VLC, mplayer and totem.

Video playback freezes at 32:08 and depending on the player freezes for 
a long time (VLC) or jumps to 33:15 with blocky things briefly on the 
screen (mplayer). If I go to 32:09, the playback continues normally. 
Rewinding back to 32:08 freezes playback again.

I am wondering if this is something that could be remedied with more lax 
error checking or somehow by jumping a few frames ahead. The problem 
appears to be confined to such a small time frame that detecting the 
problem and just jumping to the next working part would be OK.

It might be that there is an encoding problem in the video stream 
itself. However, I find it strange that such a problem would freeze the 
whole DVD playback.

My question would be, is this a libdvdread or libdvdnav problem and 
could it be possible to fix such a problem. Also, any other pointers 
towards a solution would be appreciated.


VLC -vvv output just before the freeze (such output is not encountered 
elsewhere in the log):

[0xab900828] dvdnav demux debug: DVDNAV_NOP
[0xab900828] dvdnav demux debug: DVDNAV_CELL_CHANGE
[0xab900828] dvdnav demux debug:      - cellN=13
[0xab900828] dvdnav demux debug:      - pgN=13
[0xab900828] dvdnav demux debug:      - cell_length=17420400
[0xab900828] dvdnav demux debug:      - pg_length=17420400
[0xab900828] dvdnav demux debug:      - pgc_length=221220000
[0xab900828] dvdnav demux debug:      - cell_start=180280800
[0xab900828] dvdnav demux debug:      - pg_start=180280800
[0xab900828] dvdnav demux debug: DVDNAV_SPU_CLUT_CHANGE
[0xab900828] dvdnav demux debug: DVDNAV_SPU_STREAM_CHANGE
[0xab900828] dvdnav demux debug:      - physical_wide=128
[0xab900828] dvdnav demux debug:      - physical_letterbox=128
[0xab900828] dvdnav demux debug:      - physical_pan_scan=128
[0xab900828] dvdnav demux debug: buttonUpdate not done b=3 t=1
[0xab900828] dvdnav demux debug: DVDNAV_AUDIO_STREAM_CHANGE
[0xab900828] dvdnav demux debug:      - physical=0
[0xab900828] dvdnav demux debug: buttonUpdate not done b=3 t=1

Best regards,
-- 
Tuomo Sipola
tuomo.sipola at iki.fi