[solved] DVB-T2 Recordings: Sometimes no Audio after muxing with mkvmerge (1 Viewer)

[bta489]

Hi there,

I have a strange problem with mkvmerge when processing some recordings from german DVB-T2.

So what's happening:
I record a show on my HTPC. I access the recordings from a different PC to Remux it to MKV, remove unwanted tracks and cut off the beginning and the end with mkvmerge. This usually works fine for me. However on some recordings the remuxed file will not play any audio or won't play at all (it stays on the start frame). The Raw recorded .ts-file plays without problems.

When I just remux a problematic file (keep all tracks, no edits whatsoever), the beginning will play fine up to the program announcements, when the sound cuts out, and the video continues silently. Sometimes the sound returns for the next program at the end of the recording. This appears to be limited to recordings from DasErste/ARD and related channels.

When comparing the MediaInfo of both files there are some differences in Bitrate and Codec-ID:
The Raw recording:

Audio #1
ID                          : 64 (0x40)
Menu ID                     : 137 (0x89)
Format                      : AAC LC
Format/Info                 : Advanced Audio Codec Low Complexity
Muxing mode                 : LATM
Codec ID                    : 17-2
Duration                    : 41 min 53 s
Bit rate mode               : Variable
Maximum bit rate            : 262 kb/s
Channel(s)                  : 6 channels
Channel layout              : C L R Ls Rs LFE
Sampling rate               : 48.0 kHz
Frame rate                  : 46.875 FPS (1024 SPF)
Compression mode            : Lossy
Delay relative to video     : -873 ms
Language                    : German

The edited MKV:

Audio
ID                          : 2
Format                      : AAC LC
Format/Info                 : Advanced Audio Codec Low Complexity
Codec ID                    : A_AAC-2
Duration                    : 25 min 56 s
Bit rate                    : 124 kb/s
Channel(s)                  : 6 channels
Channel layout              : C L R Ls Rs LFE
Sampling rate               : 48.0 kHz
Frame rate                  : 46.875 FPS (1024 SPF)
Compression mode            : Lossy
Delay relative to video     : 15 ms
Stream size                 : 23.0 MiB (5%)
Language                    : German
Default                     : Yes
Forced                      : No

Has anyone encountered a similar problem or even has a fix?

 

[Paul Shirley]

I have probably the same problem with UK Freeview HD. What's happening is the sound track changes format between stereo and 5.1 during the recording. Most tools detect the sound at the video start, not the cut point and throw away everything else.

You need to do a .ts to .ts cut at the point the sound track changes format before converting to any other format. I use H264TS_Cutter.exe, using the mouse scroll wheel to scrub through seems to get the position right more often. Sorry, you'll have to search for it.

If anyone has a better fix, I'll be a happy bunny to hear it.

 

[bta489]

That seems likely.

I tried the h264 ts cutter (found here) and it sort of works with HEVC/x265. The Preview has problems decoding the image, but if you know the area where to cut you can find a place. I had to change the settings (as a dialogbox suggested) to I-Frames as Cut-In-Points and All-Frames as Cut-Out-Points or else the program would crash.
The processed file however plays fine, and that is what counts. At least there is a way to process these problematic files.