TV recordings don't show correct length

[jimmy_boy]

Hi Guys,

I watch TV on my laptop using a Cinergy Hybrid T USB XS, but when I record programmes I often have problems. WMP doesn't read the correct duration in, so often a 2 hour film will show up as, say, 20 minutes. It still plays the full length of the programme, it's just when it gets to 20 minutes the slider is at the right and stays there for the rest of the programme. However if I want to seek, the slider works fine - if I put it halfway along, WMP plays from halfway through the file.

Does anyone know how to fix this?

J

[toshwriter]

Hi...

Could you give a bit more information? What version of Windows Media Player are you using? Have you tried other media players? A notable one to try would be VLC since it uses built in graphics libraries and is therefore independant of any problems associated with the Windows codecs. It's also open source!

Peter

[jimmy_boy]

Interesting - VLC seems to work fine! I also tried real player but that gave exactly the same result as WMP. WMP says the video codec it's using is "CyberLink Video/SP Decoder". Is there any easy way to change that? I'm using WMP 11.0.5721.5230. :spin:

J

[toshwriter]

Actually, it shouldn't really be a problem with the codec, but rather the demuxer that Windows uses. I'm assuming through all this your recordings are MPEG-2, directly from the TV program?

It's likely that the bitrate given in the mpeg file is incorrect. This is what the windows demuxer uses to estimate duration (it knows the size of the file, so with the bitrate it can calculate the duration). Some demuxers use more advanced techniques; I suspect this is the case with VLC since it seems to work correctly. A solution could be to just use VLC?

The problem faced by the TV recording program is that it must write the header of the file before it knows anything about the actual stream that will go into it. Generally it just writes a nominal maximum bitrate, which means the demuxer calculates the duration to be much less than it really is.

The solution would be to fix the whole file by scanning it, calculating the overall average bitrate, then rewriting the file with the new bitrate. I've come across PVAStrumento which I've heard can do this job.

[jimmy_boy]

Thanks tosh!

That seems to be what's going on, because when I run the file through PVAStrumento it comes out with the correct length in WMP. But when I play the file in WMP it's really jerky in places.:sniffle:

Is there any way I can change the bitrate in the file without chaning the actual data?

[toshwriter]

You could try a program called "DVDPatcher" which you should be able to change the nominal bitrate with. You'll have to find the actual average bitrate for the file by scanning with PVAStrumento. You can then set this in the file manually using DVDPatcher. It all seems quite long winded though!