Friday, 15 April 2011

Listening to BBC Radio Shows on an MP3 player

In the name of bastard fuck, this was far fucking harder than it had any right to be.

You have Windows Media Centre installed on your PC. Either XP, or Vista or 7. Whatever. Fine. You record DVB-T1 broadcast TV programs and watch them quite happily. You record the odd radio program (also broadcast over DVB-T1), and you can play it back on the TV. But who wants to sit around the TV listening to radio programs, what do you think this is, the 1930's?

You have recorded an audio file. You want to listen to the audio on another device. How fucking difficult do you think this is going to be? Oh, boy you are in for a fucking treat.

So, how do we do this? I should interject here and say that there is a fairly straightforwards, albeit time-consuming, way to deal with this. You fire up audacity, change the input source to be the sound card audio out, then hit record and play whatever it is you want to record. The problem with this is that you are recording a compressed track so you are going to lose quality. In my view the BBC are the experts when it comes to digital audio compression and trasmission, and it is going to spoil whatever they broadcast if I recompress it. Its like sitting in the back row of the cinema with your digital video camera. You are not exactly going to walk out with a blue ray quality version of the film are you?

First thing. If using Vista or Windows 7, media centre spits out files with the extension .wtv. These are unreadable by anything but windows, so we need to convert them into a more common format. Helpfully if you right click on the file you will find an option to convert it to dvr-ms file.

What I would then ordinarily do is fire the file up in Video Redo. This is an excellent product for taking in a dvr-ms file, cutting out all the bits you do not want (ads and so forth) and then spitting out the original video and audio streams in an mpg file. You can then happily load that mpg file into avidemux, or your editor of choice and convert it to whatever format you desire.

However, Video Redo shits itself when it is given a dvr-ms file without any video. It just cannot handle it. The more recent versions of Video Redo may be different, but I am not paying for an upgrade for something this simple.

So we want to extract the audio in some other fashion. When something is difficult, then make it harder by doing it on the command line. If we want robust command line editing tools then we want Linux. I have tried ffmpeg under ubuntu with a command that looks a bit like this:

ffmpeg -i -acodec copy -o filename.mp2

Doesn't fucking work. Apparently ffmpeg also cannot handle the earth shattering reality of a dvr-ms file without a fucking video stream.

How about:

mplayer -dumpaudio -dumpfile audio.mp2

No fucking joy. Cannot ever find an audio stream. It turns out that vlc is practically the only fucking thing on the planet that will spit the untouched audio out of a BBC Digital TV Broadcast Radio Recording. The command is this gem:

cvlc "[filename].dvr-ms" vlc://quit --sout '#transcode{vcodec=none}:duplicate{dst=std{access=file,mux=raw,dst="[filename].mp2"}}'

That's a fucking little beauty isn't it. Far more than you could ever realistically want to know about those options can be found here and here.

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