Hi,
I am running into some issues when splitting and then concatenating files
using ffmpeg.
I am using the following command line to split the files:
ffmpeg -i D:\Videos\SwP\sp.webm -codec copy -f segment -segment_time 22
-reset_timestamps 1 D:\Videos\SplitTest\swp_%04d.webm
and the output is:
ffmpeg version N-69156-gff5b9a1c Copyright (c) 2000-2015 the FFmpeg
developers
built on Jan 20 2015 00:38:00 with gcc 4.9.2 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r
--enable-gnutls --enable-iconv --enable-libass --enable-libbluray
--enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme
--enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame
--enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg
--enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr
--enable-libspeex --enable-libtheora --enable-libtwolame
--enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc
--enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp
--enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid
--enable-lzma --enable-decklink --enable-zlib
libavutil 54. 17.100 / 54. 17.100
libavcodec 56. 20.100 / 56. 20.100
libavformat 56. 19.100 / 56. 19.100
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 8.100 / 5. 8.100
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
libpostproc 53. 3.100 / 53. 3.100
Input #0, matroska,webm, from 'D:\Videos\SwP\sp.webm':
Metadata:
encoder : libwebm-0.2.1.0
Duration: 00:02:47.21, start: 0.000000, bitrate: 5728 kb/s
Stream #0:0(eng): Video: vp9, yuv420p, 1920x1080, SAR 1:1 DAR 16:9, 24
fps, 24 tbr, 1k tbn, 1k tbc (default)
Output #0, segment, to 'D:\Videos\SplitTest\swp3_%04d.webm':
Metadata:
encoder : Lavf56.19.100
Stream #0:0(eng): Video: vp9, yuv420p, 1920x1080 [SAR 1:1 DAR 16:9],
q=2-31, 24 fps, 24 tbr, 1k tbn, 1k tbc (default)
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
frame= 1648 fps=0.0 q=-1.0 size=N/A time=00:01:08.62 bitrate=N/A
frame= 3602 fps=3602 q=-1.0 size=N/A time=00:02:30.04 bitrate=N/A
frame= 4014 fps=3748 q=-1.0 Lsize=N/A time=00:02:47.20 bitrate=N/A
video:116892kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: unknown
This works fine and the time stamps are correct on the separated files. I
then take the separated files and try to merge them using the "-concat"
command. This should merge the files together into a single continuous
video without dropping any frames. I use the following command line to do
this:
ffmpeg -f concat -i D:\Videos\SplitTest\spList.txt -c copy
D:\Videos\SplitTest\swp_merged.webm
and the output is:
ffmpeg version N-69156-gff5b9a1c Copyright (c) 2000-2015 the FFmpeg
developers
built on Jan 20 2015 00:38:00 with gcc 4.9.2 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r
--enable-gnutls --enable-iconv --enable-libass --enable-libbluray
--enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme
--enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame
--enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg
--enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr
--enable-libspeex --enable-libtheora --enable-libtwolame
--enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc
--enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp
--enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid
--enable-lzma --enable-decklink --enable-zlib
libavutil 54. 17.100 / 54. 17.100
libavcodec 56. 20.100 / 56. 20.100
libavformat 56. 19.100 / 56. 19.100
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 8.100 / 5. 8.100
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
libpostproc 53. 3.100 / 53. 3.100
Input #0, concat, from 'D:\Videos\SplitTest\spList.txt':
Duration: N/A, start: 0.000000, bitrate: N/A
Stream #0:0: Video: vp9, yuv420p, 1920x1080, SAR 1:1 DAR 16:9, 1k fps,
24 tbr, 1k tbn, 1k tbc
Output #0, webm, to 'D:\Videos\SplitTest\swp_merged.webm':
Metadata:
encoder : Lavf56.19.100
Stream #0:0: Video: vp9, yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], q=2-31,
1k fps, 24 tbr, 1k tbn, 1k tbc
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
frame= 2864 fps=0.0 q=-1.0 size= 86738kB time=00:01:59.08
bitrate=5966.9kbits/s
frame= 4014 fps=0.0 q=-1.0 Lsize= 116925kB time=00:02:46.91
bitrate=5738.5kbits/s
video:116892kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 0.027859%
Where "D:\Videos\SplitTest\spList.txt" is the name of file that contains
the list of the files to merge. The command in this file is:
"file 'the 1st file location and name'"
"file 'the 2nd file location and name'"
etc.
My issue is that after the merge, the duration of the video is shorter than
the original file by 7 frames, which is the number of merges that happened
between the 8 files that came out after the split. I used mkvinfo to look
at the details of the .webm file and found that the problem is that ffmpeg
is giving the first frame of the second part of a merged video the same
time stamp as the last frame of the first part. Therefore I have duplicate
time stamps at the point of every merge and I end up loosing a frame
because of it.
Here is the FFPROBE out put for 2 frames after the merge:
...
[FRAME]
media_type=video
key_frame=0
pkt_pts=24958
pkt_pts_time=24.958000
pkt_dts=24958
pkt_dts_time=24.958000
best_effort_timestamp=24958
best_effort_timestamp_time=24.958000
pkt_duration=N/A
pkt_duration_time=N/A
pkt_pos=18554505
pkt_size=25065
width=1920
height=1080
pix_fmt=yuv420p
sample_aspect_ratio=1:1
pict_type=P
coded_picture_number=0
display_picture_number=0
interlaced_frame=0
top_field_first=0
repeat_pict=0
[/FRAME]
[FRAME]
media_type=video
key_frame=1
pkt_pts=24958
pkt_pts_time=24.958000
pkt_dts=24958
pkt_dts_time=24.958000
best_effort_timestamp=24958
best_effort_timestamp_time=24.958000
pkt_duration=N/A
pkt_duration_time=N/A
pkt_pos=18579594
pkt_size=98654
width=1920
height=1080
pix_fmt=yuv420p
sample_aspect_ratio=1:1
pict_type=I
coded_picture_number=0
display_picture_number=0
interlaced_frame=0
top_field_first=0
repeat_pict=0
[/FRAME]
...
I have tried this with a few different mkv/webm files and it happens with
all of them. I also tried it with an Apple ProRes file and it does not
occur. It looks like it is specific to ".mkv" files.
Has anyone run into this issue before? Am I missing something? I tried
looking on the forums and in the ffmpeg trac for a bug but was unable to
find anything. Any help here would be appreciated.
Thanks.
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