merging mkv(h264) pieces, slight pause in-between?

[krv]

Hi,

I am trying to re-encode an H.264 mkv file (no audio/chapters/subs) in pieces using x264. On the first encode, I seek to frame 1, and then encode say 1000 frames. On the second encode i use all of the same parameters but seek to frame 1001 and encode another 1000 frames. When doing this I was doing a 2-pass encode for each, at the same bitrate for both. Each encode would output an MKV file. When I use mkvmerge to append the second file to the first file, when I play the resulting MKV back, there is a slight jerk/pause where the two files meet... How can I fix this? and what would be the cause of this? I have also tried encoding the files to output h264 files and combining them with a simple binary file joiner, but I get the same results after putting the h264 file in an mkv and playing back...

The goal is to encode a different range of frames on 2 separate computers to complete the job quicker, then merge the resulting pieces into one seamless file.

Thanks for the input..

[krv]

NEVERMIND. I just tried splitting the original MKV with MKVMERGE first, it seems that it may be splitting it at keyframes, whereas before I was splitting them at a random frame. I then merged these pieces back together and it played seamlessly. Therefore I can just split with mkvmerge and can later re-encode each of these pieces individually with identical parameters, and without seeking (just encode the entire piece). Then I can join these files back together and the final movie should play seamlessly. duh. newbie.

[redwudz]

Most highly compressed formats have that problem. You can split anywhere, but you would need to re-encode, at least at the split point to restore the keyframe sequence. Best is to split at keyframes, but not always desired. It gets worse if you want to do a lot of cutting on a video, like removing commercials. Then you would definitely need to re-encode. Or you can convert the video to a lossless or near lossless format, do your editing, then convert back to your compressed format.

[krv]

Well i take back what I said. I had split the video using mkvmerge and the re-combined the parts and it was all smooth, however, when I actually re-encoded each of the parts and then recombined those re-encoded parts, the pause/jerk was still present...

[poisondeathray]

Just a hunch - When you re-encode, you change the frametype distribution. But when you split, each split is right before an IDR-frame (so each segment after the 1st will always begin with an IDR frame) . However, when you re-encode, frame 0 might not be an IDR-frame (it might be placed later on in coding order). A decoder cannot begin decoding that new section until the that IDR frame is reached (so it has to find that IDR frame, and then go backwards - this might cause a pause). You can force frame 0 of each newly encoded split section to be an IDR frame with a qpfile

The more segments you use, theoretically the more deviation from a regular 2-pass encode - it gets less efficient (lower quality at the same bitrate) because of the change in GOP characteristics

Also, have you tried other builds (maybe you mkvmerge build is buggy) , or maybe mp4box ? and have you tried other players?