Rockbox mail archiveSubject: Re: recording problem
Re: recording problem
From: Dave Chapman <dave_at_dchapman.com>
Date: Tue, 04 Jan 2005 16:56:01 +0000
An ".mp2" file that normal audio players can handle is known as an "MPEG
elementary stream". Multiple elementary streams (video, audio and data)
are normally "multiplexed" together to form MPEG program streams or
transport streams. Even if the file only contains a single audio
stream, it's perfectly valid to store that in a program stream or
It sounds to me as if your DVB recording software is doing that -
recording it as an MPEG Program Stream or similar, and not as an
elementary file. ffmpeg is simply extracting the audio data from MPEG
file and saving it to a seperate file - lots of tools exist to do that.
So these pops and squeaks are probably not errors, just the fact that
the file format is not what your audio player is expecting. The actual
error correction is done inside the card and/or driver - applications
don't touch it.
> If you do rip DVB, you may find that yu have horribly pops and squeaks
> all over it.
> If so, the piece of software you need to correct these errors (apply the
> EC in the transport layer) is ffmpeg ...just mention this as it took me
> some 10 hours to work out what needed to be done and then track down a
> bit of software to do it.
>> I can't comment on your Rockbox problems, but if you are serious about
>> recording radio, I would definitely recommend buying either a DAB or DVB
>> (either satellite or terrestrial) receiver card for your PC.
>> DAB (and DVB) radio broadcasts using "MP2" compression which is similar
>> to MP3. PC receivers are able to save this MP2 data directly to a file,
>> and your Archos will happilly play back those MP2 files in the same way
>> as MP3 files. Apart from ease of use, you are also getting a broadcast
>> quality recording - listening to the MP2 data via your Archos will be
>> the same quality as listening to a live broadcast.
>> This was the main reason I bought my Archos - to listen to the MP2 radio
>> recordings I make.
>> rinty wrote:
>> > Hi all, Over the Christmas period, I've tried to record a couple of
>> > radio programmes from my DAB radio to my archos recorder V2, (with the
>> > FM radio) using an analogue connection. In both cases, I've tried to
>> > record an 8 hour long programme. The recordings have started OK,
>> > however after an hour the second time, and about 4 hours the first,
>> > the recordings have become seriously degraded. In the first case, it
>> > sounds as though there's major clipping on the bass notes of the
>> > recording. I thought at first, that the recording level was too high,
>> > however there doesn't seem to be a way of adjusting this, certainly
>> > not through speech. In the second case, the recording keeps loosing
>> > bits. I.E. there's half a second of sound, and then variable blank
>> > spaces, up to half a second.
>> > I'm totally blind, so am using rb with the voiced menus and so on.
>> > In the past, I've done lots of recording, with no problem, including a
>> > bit from the DAB radio. This is however the first time that I've
>> > attempted to record music on the RB through the radio, though I've
>> > done it from audio streams from the internet.
>> > Thanks,
>> > Rob
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Received on 2005-01-04