As it so happens, I own a DVR device that will record DVB-S and DVB-S2 TV into segments of a MPEG transport stream.
For DVB-S2 HD programs, the stream already contains h.264 compressed video. However since we don't live in the 80's anymore where there used to be a thing called VPS that would make sure your VCR starts and stops when the program does – even if that does not match the time printed in the program guide – the recording will be enclosed by parts of the surrounding broadcast.
Getting rid of that "garbage" is a bit tedious, but here's how I managed.
The receiver writes files
00001.ts,
00002.ts...
00012.ts of one gigabyte each to the attached USB drive. So first turn that into one nice big file by using cat (the target better be ext4 or something else that can handle 2G+ files).
cat *.ts > <name>.ts
Now the problem is we can't just use a media player and seek to the cut points because the data in this transport stream is not properly timestamped.
But first we need to figure out which streams (tracks) are present in the raw material. Often broadcasters transmit a bunch of redundant audio streams. Just in a single language of course, apparently to make sure viewers are not getting too much value for their license fee.
$ ffprobe <name>.ts
[...]
Stream #0:0[0x18a6]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 50 fps, 50 tbr, 90k tbn, 100 tbc
Stream #0:1[0x18b0](deu): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, s16, 256 kb/s
Stream #0:2[0x18b1](mis): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, s16, 192 kb/s
Stream #0:3[0x18b3](mul): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz, stereo, s16, 192 kb/s
Stream #0:4[0x18b2](deu): Audio: ac3 ([6][0][0][0] / 0x0006), 48000 Hz, stereo, s16, 448 kb/s
Stream #0:5[0x18ba](deu): Subtitle: dvb_teletext ([6][0][0][0] / 0x0006)
In this case, I'm only going to keep streams 0:0 (the h.264 video) and 0:4 (the AC3 audio). You can use
mplayer with the
-aid/
-vid options to check out the various streams. To play the file with audio stream 0:3 for example, run as
mplayer -aid 0x18b2 <name>.ts
So now to get a seekable file with only the wanted streams, do this:
ffmpeg -i <name>.ts -f mpegts -c copy -bsf:v h264_mp4toannexb -map 0:0 -map 0:4 <intermediate>.mkv
Then open the file e.g. in
gnome-mplayer, seek to the start and the end of the actual content and make note of the timestamps.
Finally, fire up
mmg (mkvmerge GUI), and
add the freshly created
<intermediate>.mkv file on the
Input tab.
Then switch to the
Global tab and enter the title of the recording into the
File/segment title field.
Now check the
Enable splitting... checkbox and select
...by parts.
Enter the begin/end timestamps noted down earlier into that field, separated by dash like 00:06:45-2:19:31.
Now verify that the
Output filename is to your liking and hit the
Start muxing button.
