MPEG-4 ASP / Xvid with B-frames plays in wrong frame order ("ping-pong" effect) #212

MPEG-4 ASP / Xvid with B-frames plays in wrong frame order ("ping-pong" effect)

Environment

• QuickLook Video: tested with 3.11 and 3.12
• macOS 26
• Apple Silicon M4
• Video container: AVI
• Video codec: MPEG-4 Advanced Simple Profile (Xvid)
• Audio: MP3

Problem

AVI/Xvid videos containing B-frames do not play in the correct presentation order through Quick Look / QuickTime.

The video progresses normally in time, but individual frames repeatedly jump backwards and forwards, producing a very characteristic "ping-pong" effect.

The same AVI plays perfectly in IINA/mpv/FFmpeg.

Investigation

I tested an AVI containing:

Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658)
640x272
24000/1001 fps
Audio: MP3, 48000 Hz, stereo, 128 kb/s

First I used:

-bsf:v mpeg4_unpack_bframes

while copying both streams without re-encoding.

The resulting AVI still exhibits exactly the same ping-pong behaviour in Quick Look.

Therefore this does not appear to be caused specifically by packed B-frames.

I then inspected the timestamps. A remuxed sample shows this packet sequence:

PTS       DTS
0.042     0.001
0.125     0.042
0.083     0.083
0.167     0.125
0.250     0.167
0.209     0.209
0.292     0.250
0.375     0.292
0.334     0.334

So the stream requires normal B-frame reordering from decode order to presentation order.

Important A/B test

I re-encoded the first 60 seconds of exactly the same AVI back to Xvid, but explicitly disabled B-frames:

ffmpeg \
-i "input.avi" \
-t 60 \
-map 0:v:0 -map 0:a:0 \
-c:v libxvid \
-bf 0 \
-q:v 4 \
-c:a copy \
"output-no-bframes.avi"

Result:

I also previously tested replacing only the MPEG-4 ASP video with H.264 while keeping the same AVI container and MP3 audio. That also plays correctly.

Possible cause

This strongly suggests that the problem is not Xvid decoding itself, nor the AVI container, nor MP3 audio.

It appears to be related specifically to B-frame presentation reordering for MPEG-4 ASP/Xvid through the Media Extension / AVFoundation path.

The behaviour visually looks as if frames are being presented in decode/DTS order rather than correctly reordered into presentation/PTS order.

I noticed that QuickLook Video contains support related to frame reordering (requiresFrameReordering, maxBFrames and the MESampleCursor reordering methods), so perhaps the MPEG-4 ASP case is exposing an issue in this path.

Version observation

With QuickLook Video 3.11, MKV playback works normally for me, while the AVI/Xvid B-frame issue above remains.

After updating to 3.12 I additionally experienced problems with MKV preview, so I temporarily returned to 3.11 while investigating the AVI/Xvid issue.

I would be happy to perform additional FFmpeg/ffprobe tests if useful.