Is this possible?

[Muse]

I made two recordings of the same thing to MP3. They were of a ~ 3 hour radio program, stereo recordings. One I made at home off my receiver using 128 mbps sampling rate, 32 khz frequency. The other recording was made in the air studio of the radio station using 128 mbps sampling rate, 44.1 khz frequency. As fate would have it ( :| ) both recordings were screwed up. The one I made at home had left channel only, evidently because of a bad RCA plug connection for the right channel. The recording I made in the air studio was OK for the first ~ hour and then the left channel cut out, evidently also a bad RCA plug connection. So, I have two MP3 recordings of the same 3 hour broadcast but one has left channel the whole way through and the other has the right channel all the way through. They don't begin and end at precisely the same moment.

My question is this: Is it possible to create a 3rd MP3 file with one channel from each of the others? This would only work if there's a way I can synch the channels, obviously. If they are 1/4 second off, it will be necessary to tweak the channels to get them to synch up. I know it's probably very hard to do, but maybe there's a reasonably easy way.

 

[Muse]

What occurs to me now is maybe use Protools. We use it at the radio station. I don't know if Protools (we use version 6.x on the Mac) will import MP3s but I could convert them to WAV, which I know that Protools can deal with. Then I can synch the channels in there and bounce to a WAV that I can later convert to MP3. So, I guess it's doable... Don't know if I will lose any quality with the conversions, but I guess I can try and see. Not sure if Protools can deal with 3 hour long files... Comments?

 

[MagnusTheBrewer]

CakeWalk, Sound16 and, Premiere are a few of the programs I have used that can do this.

 

[Muse]

Originally posted by: MagnusTheBrewer
CakeWalk, Sound16 and, Premiere are a few of the programs I have used that can do this.

Thanks. Can they deal on this level with MP3s or would I have to convert first to WAV? Are any of these freebies?

 

[videogames101]

Originally posted by: Muse

Originally posted by: MagnusTheBrewer
CakeWalk, Sound16 and, Premiere are a few of the programs I have used that can do this.

Thanks. Are any of these freebies?

audacity

 

[Muse]

Originally posted by: videogames101

Originally posted by: Muse

Originally posted by: MagnusTheBrewer
CakeWalk, Sound16 and, Premiere are a few of the programs I have used that can do this.

Thanks. Are any of these freebies?

audacity

Thanks. Can this deal with the fact that the two files were recorded at different sampling rates:

File one:
128 kbps bitrate
32 khz sampling rate

File two:
128 kbps bitrate
44.1 khz sampling rate

Edit: I already have Audacity installed and I am simultaneously opening both files. It's taking a while (longest 4 minutes of my life... it's been about 15 minutes now and still ~ 3 minutes to go!). Will see what I see.

 

[Muse]

I've got both files in the same session of Audacity now and they are nearly synched up. However, one of the files is playing at an advanced speed. I mute one and play the other. The file recorded at 32 khz frequency is playing at least 1 1/2 times speed. Sounds like a 33 RPM record played at 45 RPM or maybe 66 RPM! Any clue what's up with that? Also, the file isn't as long. Naturally it takes up less time because it's playing at an advanced speed. Sounds like the Chipmunks!

Edit: I'm thinking the only way I'm going to get this to work is to convert the MP3s to WAV files first. Otherwise Audacity is going to convert the 32 khz file to a 44.1 khz file and it'll play like a 33 RPM record at 44.1 RPM!

 

[ChAoTiCpInOy]

Aren't most radio channels broadcasted in Mono?

 

[Muse]

Originally posted by: ChAoTiCpInOy
Aren't most radio channels broadcasted in Mono?

Each channel is mono, there's two channels so it's stereo. It's called FM multiplex, I think.

Well, I tried again, I guess reversing the way I did it before. Audacity has one instance but you can open two files and they are opened in different sessions of the same instance. I created a 2nd stereo track in one, copied the tracks in the other and pasted back to the first. The first time I did this I got one that played 1.5 times too fast, but the 2nd time I believe I reversed the order (pasted the 2nd on the 1st instead of the other way around) and this time they both played the right speed. I then split one stereo track into two separate tracks and deleted the channel that cut out after an hour. Then I had a right and left channel, one from each separate recording. They sound good together. The problem now is that after a stretch of time (say, an hour) the synch is off by a split second and it doesn't sound right. In Pro Tools I am pretty sure you can stretch a track out, but I don't know if I can do it in Audacity. I can at least listen to the entire 3 hour show now if I stop several times to resynch, but I'd really like to synch the whole thing and save a new file that can be listened to from beginning to end. I wonder why they don't play at the same speed (i.e. why the simultaneous play of the two tracks loses synch after a while). I mean they were broadcast and recorded at the same time, theoretically the synch should be constant from beginning to end.

 

[Muse]

I'm still working on it. Audacity has a function where you can change the tempo of a track (without changing the pitch). It's pretty granular -- you can change it in increments of 0.001 of a percent. It appears you can even change the length of a track by 0.1 seconds. It's hit and miss, but I think it may work. The problem is that Audacity sometimes takes a ton of time to finish processing and I'm getting long long long hourglasses and have to do something else (ATOT!) while it refreshes. If the processing were quicker, I would have finished last night. I've already spent over 4 hours working on this. I guess that Pro Tools has a good reason for the hardware side of their business. I assume that hardware is to add muscle to the process that just isn't there with a PC or Mac.

 

[Modelworks]

Save yourself the headaches and just convert each file to a wav file.
Then join and re-compress.
Shouldn't even take an hour on a decent pc.

Working with compressed formats in video or audio is usually trouble.

 

[Muse]

Originally posted by: Modelworks
Save yourself the headaches and just convert each file to a wav file.
Then join and re-compress.
Shouldn't even take an hour on a decent pc.

Working with compressed formats in video or audio is usually trouble.

I actually did convert the MP3s to Wav (using Total Recorder Standard Edition, v. 7.1). They were WAV files, but they were seen in terms of their having MP3 parameters (e.g. 128 kbps, 44.1 khz). I opened them in Audacity simultaneously, copied and pasted one of them into the other Audacity session and shifted one until one end synched up. The other end was off by a split second. Doing a change tempo on one track several times managed to get them very very close to synching on both ends, close enough I think, and I'm right now exporting to a WAV file and will export again to an MP3 file and see what I have. I think it's actually acceptable. Amazingly, I'll wind up with an MP3, one channel having been recorded at home off my receiver, the other having been recorded off the radio station's air board! This even though one channel is 44.1 khz frequency and the other 32 khz frequency. The file may not play on my Sansa m250 MP3 player, but I'll be able to listen to it on my computer. I'll take it.

 

[Muse]

Ach, the WAV export only sounds in the right channel. I may have to listen to this thing with Audacity itself on the computer. I'm exporting to MP3 now anyway just to see what's up. Have only tested on my PC, not my MP3 players, one of which can also play WAVs, but it doesn't look promising.

Edit: Correction! I'd forgotten that one track started about 3 minutes before the other, so that's why I thought it was just one channel. There's still a synch problem, more obvious when listening with headphones. This is a hassle. Why aren't the tracks the same length to begin with? I'm sure there's a simple explanation...

 

[Muse]

I'm giving up. Using Audacity, I managed to get both tracks synched beginning to end and thought I had the holy grail in my pocket. I'd tweaked the right channel using Effects/Change Tempo until it was the same tempo as the left channel, magnified until I could shift to get perfect (well almost) synch. At that point I could listen to the whole 3 hour recording in Audacity. I exported this to MP3, but the resulting MP3 is not synched! It's impossible to listen to! The two channels are unsynched by something like 1/4 second. I have to assume that it's a shortcoming of Audacity. I could bring it all into the radio station and work on it in Pro Tools but think I'll just resign myself to listening to it in Audacity and chalk it up the experience and bad luck. It was fun to mess with Audacity, but there were incredibly aggravating wait times. I'm not blaming the program for that, but the inability to export properly I have to think is due to bad code. Maybe I should contact the developers...

 

[corkyg]

What you are really asking is can MP3 files be concatenated (chained together), and if so, how to do it. If you Google Concatenate MP3 files, you will see many choices. This is a good one for techies:

Chain

 

[Muse]

Originally posted by: corkyg
What you are really asking is can MP3 files be concatenated (chained together), and if so, how to do it. If you Google Concatenate MP3 files, you will see many choices. This is a good one for techies:

Chain

Well I don't think that it's actually concatenation, which I think is making one follow the other. In this case, I have the right channel from one file and the left channel from the other and wanting to join them into one file. There's about a 3 hour portion of each which is of the same radio broadcast. One starts 3 minutes before the other and that file lasts about 5 minutes longer as well. My intention, of course, is to chop off the beginning and the end and have 3 hours of stereo. It's a pretty iffy proposition, partly because the devices although recording the very same thing aren't precise instruments and the results aren't natively synchable. I tried to adjust one to be a fit for the other, but I don't know if this is really possible. Eh, I think I'll just listen to the thing in Audacity and when I can't stand the sound, just make a minor adjustment. 5-6 such adjustments over a 3 hour period should be all the hassle involved with a one-time listen that's reasonably satisfactory.