Combine mp2 and mp3: output format and preferences?

Hi all,

I have two audio files, one is mp2 and the other is mp3, which I would like to combine in the following way: I would like to replace some parts of the mp2 track with the corresponding parts of the mp3 track. The track details are as following:

Codec: MPEG 1 Audio, Layer 3 (MP3)
Channels: Stereo
Sample rate: 44100 Hz
Bitrate: 128 kbps

Codec: MPEG 1 Audio, Layer 2
Channels: Stereo
Sample rate: 48000 Hz
Bitrate: 192 kbps

I have a DVD from which I extracted the mp2 track and I would like to replace this original track with the new, combined track (mp2 + mp3). Now my questions:

  1. What should I set the sample rate to for this new combined track, 44100 Hz or 48000 Hz? What about the resulting bitrate, does it need to be modified as well? What is best for a DVD format?
  2. Do I need to do any format conversions before editing the tracks in Audacity? If yes, what needs to be converted?
  3. Which format should be best to save the combined track to, mp2, mp3 or something else? Will this format be compatible with the DVD I extracted the original track from (was mp2 from the beginning)?

I am a newbie when it comes to Audacity and sound editing and I hope that somebody can give me a helping hand.

Thank you in advance.

Kind Regards,

Use Audacity 1.3.12 (the old 1.2.x version has limited ability to handle more than one sample rate in the same project and could easily mess things up)

The standard sample rate for DVD is 48 kHz (48000 Hz)

MP2 and MP3 are both “lossy” formats, which means that when audio is encoded into either of these formats there will be some loss of sound quality. Whenever possible it is best to work with uncompressed audio formats such as WAV.

In Audacity 1.3.12 you can import both of the files - each will appear on it’s own track. If you keep the files on their own tracks then you can cross-fade from one to the other which will produce a smooth, click free edit.

This is a cross-fade:
You can move sections of a track by splitting the track (Edit menu), then using the “Time Shift” tool (double headed arrow <–>) to slide sections left/right along their track.

Thank you so much for your reply Steve, I will have a look and come back in case I have more questions.
My main doubt was what the sample rate and the format of the exported track should be but I think I have a better picture now.

Thanks again.

Kind regards,

To set the sample rate for the “Project”, and hence the sample rate that will be used for the finished audio file when you Export, set the “Project Rate” in the bottom left corner of the main Audacity window. Note that by default the project rate will be whatever is set in “Edit menu > Preferences > Quality”, but if you import a file into an empty project, the sample rate of the imported file will override the default sample rate that is set in preferences. It’s always worth checking the Project rate in the lower left corner before you export.

Hi again Steve,

thank you for the tip about the project sample rate, however, speaking of the sample rates, I have a new problem, or at least I think I do.

As I mentioned, the two audio files have different sample rates (mp2 = 48000 Hz, mp3 = 44100 Hz). The original sound is the mp2 file and this is how I am trying to replace part of it with the ones from mp3 file:

Import mp2 file in Audacity (File → Import → Sound)
Open the mp3 file in a separate window (File → Open)

Now I would like to select and copy 4 minutes of mp3 clip and replace the corresponding part (at the same offset in time and with the same length) in the mp2 clip.
Before I do this, I select this part of mp2 file and delete it (Edit → Delete). Then I copy and paste the mp3 part into the mp2 file at the same point I previously deleted the part (Edit → Paste)

However, when playing the cut-in part, the playback is much faster than for the rest of the original mp2 audio and I guess it is because of the varying sample rates, true?

I don’t know how to modify the sample rate of mp3 file before I copy and paste it to mp2 file so that it is played at the same speed as the mp2 clip.

Would you happen to know what I am doing wrong?

Thanks again Steve.

Kind Regards,

  1. Upgrade to Audacity 1.3.12.
  2. Open Audacity and import both files (into the same project).
  3. No need to put the clips into the same track - Audacity is a multi-track editor, designed to work with multiple tracks at the same time.
  4. See my previous post for some hints about editing.