Chopped playback in HDV, near edited cuts

[benoitm]

I perform simple "cut" edits on a HDV (MPEG2) file using either Womble MPEG Video Wizard or Avid Liquid 7.1, then export with no conversion; the original HDV file is digitized from a SONY HDV cam.

The exported .mpg file (still HDV i.e. 25 Mbps 1080/50i) plays fine in VLC except near the cuts: the video plays a bit choppy at these points. I suspect the edits have made small GOP changes that fool VLC (8.6 and 8.5).

Note: Windows Media Player 11 plays back the same file without a glitch.

Would it be possible to have a look at this issue ?

The two applications used for testing (Womble & Avid Liquid) are not exactly random shareware, and both do not touch the MPEG GOP except near the cuts

[DJ]

Editing is supposed to occur on key frames (See your editors help file as to how to do this). Post processing can also help this issue.

[benoitm]

I would like to revive this thread:

I now have updated my system: on the software side, I use now AVID LIQUID 7.2, which includes a number of bug fixes a.o. in the MPEG2 export area. On the hardware side, I have a E6700 Core2Duo CPU & a ATI X1950Pro GPU with Catalyst 7.7 drivers.

I still have that same problem:
Original HDV rushes (.m2v) play nicely with VLC (Win32) 0.8.6c - WinXP Task manager reports CPU usage near zero (I assume the GPU is doing the decoding job).
But when I edit these HDV rushes in AVID Liquid 7.2, then use the Export to MPEG2 function (keeping HDV resolution & bitrate, i.e. 1440 x 1080i, 25 Mbps CBR), the resulting file clearly drops frames after each scene change (corresponding to cut edits); this is not a CPU saturation issue, as CPU utilization remains near zero. The VLC message window reports many errors.
However, the same MPEG file plays fine in other players (WMP11 with a ARCSoft MPEG decoder...) and WM Encoder or TMPGEnc happily convert this file without frame loss or other complain.

Note that tools like MediaInfo & GSPOT don't show any problem with this MPEG2 file (nor with the original .m2v files)

I really would like to understand where the problem is:
Does VLC have a problem decoding some HD MPEG2 files ?
Does Avid Liquid 7.2 produce "illegal" MPEG2 HD files ?
Let me know what info you need (sample VLC message output, short problematic MPEG2 test file, ...)

[benoitm]

Hmmm, doing some further tests, I noticed that running VLC on another WinXP partition (with other MPEG decoder installed), the problem disappears !

So: my question: isn't VLC independent of the installed MPEG decoder ?
What would cause VLC to playback the same HD MPEG2 file fine in one WinXP partition and choppy in another one ?

tx for any hint

[Jean-Baptiste Kempf]

Try to force the use of the ffmpeg mpeg-2 decoder:
--codec ffmpeg

[benoitm]

means I need to install ffmpeg...
does it work fine with HD MPEG (i.e. 25 Mbps MPEG2) ?

[benoitm]

I still have the above problem (even in my "other" WinXP partition, unlike what I stated earlier)

Maybe this kind of errors, found in the event window during an "offending" file playback, can help t'shoot ?

libmpeg2 debug: 1440x1080 (display 1440,1080), aspect 768000, sar 4:3, 25.000 fps
main warning: dts != current_pts (152878)
main error: decoder is leaking pictures, resetting the heap
main warning: backward_pts != current_pts (-40000)
libmpeg2 debug: 1440x1080 (display 1440,1080), aspect 768000, sar 4:3, 25.000 fps
main warning: dts != current_pts (-42122)
main warning: vout synchro warning: pts != current_date (-40000)


Reminder: the "offending" files are .mpg (PS) files created by Avid Liquid 7.2 using the Export (MPEG-2) function, with "HDV2" settings (i.e. 1440x1080/50i MP@HL PAL 25 Mbps & 224 Kbps MPEG-1 Layer2 audio)

When instead of exporting a .mpg PS file, I use Avid Liquid's "FUSE" tool, the resulting .m2v (ES) plays without any problem.

I'm still looking for hints: who is the culprit ?

[benoitm]

Help anyone !

Am I the only one to have problems with VLC when playing back HD MPEG-2 files (edited from HDV material and output by Womble MPEG Video Wizard or AVID Liquid 7.2) ?

Note: I have verified that this problem occurs with multiple HD (1440x1080i) .mpg (ps) files, on different Win XP machines and also on Ubuntu Linux.

Thanks