A framerate problem after adding a -500 ms delay to audio

[loninappleton]

Hello,

   I'm watching an mkv to which I adjusted minus -500 ms to the audio.  But it stays in synch early in the playback and then goes off.  How do I check the framerate or set as 'constant' playback option if needed?  I cannot find the entry where AVIDemux stores the framerate of a saved MKV. 

  Please give detailed steps from loading the MKV.  I've seen where a tutorial says look under Video but still did not locate an entry for framerate.  I will supply the MediInfo in an Attachment.

[eumagga0x2a]

But it stays in synch early in the playback and then goes off.

Do you speak about playback in Avidemux or playback in a video player?

If the former: Does video play faster than audio or vice versa? If video lags behind, it might be due to performance constraints of the hardware (it must be a really ancient hardware to fail to play 1040x586 @ 25fps in real time, however) or the unaccelerated video output chosen in Avidemux ("Qt" instead of "DXVA2" or "OpenGL").

Otherwise I'd suspect that the frame rate of the video is simply wrong.

I cannot find the entry where AVIDemux stores the framerate of a saved MKV.

MediaInfo detects 25 fps as effective frame rate:

Code Select Expand

Frame rate mode                          : Constant
Frame rate                              : 25.000 FPS
Matroska technically doesn't store a frame rate. It uses a so-called default duration (which specifies how long a player should show a frame of the video if presentation timestamps are missing), normally all pictures have valid presentation timestamps with accuracy of one millisecond.

I've seen where a tutorial says look under Video but still did not locate an entry for framerate.

I don't follow you, I fear. What tutorial do you mean?

By the way,

Code Select Expand

Width                                    : 1 040 pixels
Height                                   : 586 pixels
Using height (or width) which is not a multiple of 16 should be carefully evaluated and, if possible, avoided as it worsens compressibility.

[eumagga0x2a]

Otherwise I'd suspect that the frame rate of the video is simply wrong.

In this case (if video is faster than audio), you could try to add "Change FPS" video filter converting from "25 (PAL)" to "23.976 (Film)" and re-encode a short stretch of the video to see whether this is enough to ensure proper sync.