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KpeX · 7th January 2004, 22:48

MP3 FAQ
MPEG-1 Layer 3 encoding and playback

1. What is MP3?

MP3, also known is MPEG-1 Layer 3, is a general purpose lossy encoded audio format capable of high compression rates retaining considerable quality. Layer 3 is not a new version of MPEG Layer 1 or Layer 2, but a different complexity level. There are many MP3 encoders available, the highest quality encoder is Lame, which is also free and open-source.

The Lame encoder version 3.9x is highly recommended over any other MP3 encoder.

2. Does MP3 support more than 2 channel audio?

The MP3 specification does technically support multichannel, but implementations are rare and compatibility is unsure. Keep in mind that you can encode your multichannel source with a pro logic (II) downmix into stereo MP3. Fraunhofer has made (a 5.1 MP3 encoder/decoder demo available), although this is not a true 5.1 implementation but rather a backwards-compatible matrixed format.

[The link is broken, and the format is deprecated]

3. Can the volume of an MP3 be raised up without reencoding?

Yes, there are few programs that offer this, check mp3gain & mptrim for instance.
BeSplit offers this as well. for commandline, read q5 in the MP2 FAQ.

4. How can I achieve good quality results with MP3?

For movie soundtracks 128kbps and above will usually have acceptable quality. To increase quality, use VBR and joint stereo. The recommended commandline for transparent quality with the Lame encoder is -V2 (which can be used in BeSweet (-V settings require lame 3.94 or later). The recommended version is lame 3.97. This preset will result in transparency with the vast majority of samples, and usually a bitrate of 140-170 kbps for movie soundtracks.

[Of course the versions are updated until 3.100, and ffmpeg are updated also (now Lavc59.9.100 libmp3lame), and can encode mp3 with -aq 2, equivalent to -V2 for Lame]

5. What version of Lame is included with BeSweet?

The latest versions of BeSweet now include Lame 3.90.3, the previously recommended version. Recent full packages of belight include lame 3.97; this version is highly recommended for quality, see Q8 for more information. As mentioned before, any lame encoder version 3.9x is a good quality choice. Most lame users are using the latest stable version or 3.97.

[Now the last version is 3.100]

6. My VBR MP3 file shows the wrong length. How can I fix this?

If you are determining the playback length from a DShow based player such as WMP or ZoomPlayer, the wrong length is because of the buggy Microsoft MP3 Dshow filter that comes with windows. Ignore it or use a good non-dshow player such as winamp.

If the length still appears to be wrong, use BeSplit, with the following command :

Code:

BeSplit -core( -input c:\track.mp3 -prefix c:\track -type mp3 -fix )

This solution is also good for wrong-reported-length wav files. just switch "-type mp3" with "-type wav".

[The players can't know the correct duration of VBR files if not exist a special header field than inform of that.
If the mp3 was make VBR but without that info it is not possible know the full lengh without read the full file.
The same with AAC VBR files, we need put in a m4a container to insert that info]

7. Why is my MP3 destination file downsampled to 32kHz or lower?

In latter versions of LAME(3.9x), it will automatically downsample audio for low bitrates(<128kbps) to reduce artifacts.

8. Where can I find lists of recommended MP3 settings?

List of recommended LAME settings

9. Will encoding to MP3 with joint stereo preserve Pro Logic/Pro Logic II information?

Lame, the only recommended MP3 encoder, uses a high quality M/S (mid/side) joint stereo mode, which is much better than the intensity stereo used by the joint stereo mode of many other encoders like MP2. Due to the way that DPL surround channels are matrixed into the two stereo channels, this M/S joint stereo mode is actually recommended when using Pro Logic. Additionally, the --alt-presets are highly recommended for DPL. See a more detailed explanation here.

10. How can I properly mux a VBR MP3 into AVI?

Use VirtualDubMod or Avi-Mux GUI.

[Of course ffmpeg can do the job also, but formerly the avi container not support audio VBR and is always recommended mux in mkv container:
ffmpeg -i input.avi -i vbr.mp3 output.mkv
Or use MkvToolNix]

11. What about encoding MP3 under Linux/*nix?

Lame, the most recommended MP3 encoder, builds under GNU/Linux and a host of other platforms. Grab the source from sourceforge, or get rpms from rpm.pbone.net or debian builds from (www.rarewares.org/debian.html)

Once lame is installed, mencoder, part of the mplayer project, has an mp3 encoding module based on lame. Simply reconfigure and rebuild your mplayer source, and when encoding with mencoder you'll be able to encode to mp3 using the -oac mp3lame options. For more information see the mplayer man page under the 'codec specific encoding options' section.

[I not found the rarewares link, I'm not a linux user but see in https://lame.sourceforge.io/ , and ffmpeg work also in Linux (Debian, Ubuntu or Fedora pakages)]

7th January 2004, 22:48	#4 \| Link
KpeX Registered User Join Date: Jun 2003 Location: Great Lakes, USA Posts: 1,433	MP3 FAQ MPEG-1 Layer 3 encoding and playback 1. What is MP3? MP3, also known is MPEG-1 Layer 3, is a general purpose lossy encoded audio format capable of high compression rates retaining considerable quality. Layer 3 is not a new version of MPEG Layer 1 or Layer 2, but a different complexity level. There are many MP3 encoders available, the highest quality encoder is Lame, which is also free and open-source. The Lame encoder version 3.9x is highly recommended over any other MP3 encoder. 2. Does MP3 support more than 2 channel audio? The MP3 specification does technically support multichannel, but implementations are rare and compatibility is unsure. Keep in mind that you can encode your multichannel source with a pro logic (II) downmix into stereo MP3. Fraunhofer has made (a 5.1 MP3 encoder/decoder demo available), although this is not a true 5.1 implementation but rather a backwards-compatible matrixed format. [The link is broken, and the format is deprecated] 3. Can the volume of an MP3 be raised up without reencoding? Yes, there are few programs that offer this, check mp3gain & mptrim for instance. BeSplit offers this as well. for commandline, read q5 in the MP2 FAQ. 4. How can I achieve good quality results with MP3? For movie soundtracks 128kbps and above will usually have acceptable quality. To increase quality, use VBR and joint stereo. The recommended commandline for transparent quality with the Lame encoder is -V2 (which can be used in BeSweet (-V settings require lame 3.94 or later). The recommended version is lame 3.97. This preset will result in transparency with the vast majority of samples, and usually a bitrate of 140-170 kbps for movie soundtracks. [Of course the versions are updated until 3.100, and ffmpeg are updated also (now Lavc59.9.100 libmp3lame), and can encode mp3 with -aq 2, equivalent to -V2 for Lame] 5. What version of Lame is included with BeSweet? The latest versions of BeSweet now include Lame 3.90.3, the previously recommended version. Recent full packages of belight include lame 3.97; this version is highly recommended for quality, see Q8 for more information. As mentioned before, any lame encoder version 3.9x is a good quality choice. Most lame users are using the latest stable version or 3.97. [Now the last version is 3.100] 6. My VBR MP3 file shows the wrong length. How can I fix this? If you are determining the playback length from a DShow based player such as WMP or ZoomPlayer, the wrong length is because of the buggy Microsoft MP3 Dshow filter that comes with windows. Ignore it or use a good non-dshow player such as winamp. If the length still appears to be wrong, use BeSplit, with the following command : Code: BeSplit -core( -input c:\track.mp3 -prefix c:\track -type mp3 -fix ) This solution is also good for wrong-reported-length wav files. just switch "-type mp3" with "-type wav". [The players can't know the correct duration of VBR files if not exist a special header field than inform of that. If the mp3 was make VBR but without that info it is not possible know the full lengh without read the full file. The same with AAC VBR files, we need put in a m4a container to insert that info] 7. Why is my MP3 destination file downsampled to 32kHz or lower? In latter versions of LAME(3.9x), it will automatically downsample audio for low bitrates(<128kbps) to reduce artifacts. 8. Where can I find lists of recommended MP3 settings? List of recommended LAME settings 9. Will encoding to MP3 with joint stereo preserve Pro Logic/Pro Logic II information? Lame, the only recommended MP3 encoder, uses a high quality M/S (mid/side) joint stereo mode, which is much better than the intensity stereo used by the joint stereo mode of many other encoders like MP2. Due to the way that DPL surround channels are matrixed into the two stereo channels, this M/S joint stereo mode is actually recommended when using Pro Logic. Additionally, the --alt-presets are highly recommended for DPL. See a more detailed explanation here. 10. How can I properly mux a VBR MP3 into AVI? Use VirtualDubMod or Avi-Mux GUI. [Of course ffmpeg can do the job also, but formerly the avi container not support audio VBR and is always recommended mux in mkv container: ffmpeg -i input.avi -i vbr.mp3 output.mkv Or use MkvToolNix] *11. What about encoding MP3 under Linux/nix?** Lame, the most recommended MP3 encoder, builds under GNU/Linux and a host of other platforms. Grab the source from sourceforge, or get rpms from rpm.pbone.net or debian builds from (www.rarewares.org/debian.html) Once lame is installed, mencoder, part of the mplayer project, has an mp3 encoding module based on lame. Simply reconfigure and rebuild your mplayer source, and when encoding with mencoder you'll be able to encode to mp3 using the -oac mp3lame options. For more information see the mplayer man page under the 'codec specific encoding options' section. [I not found the rarewares link, I'm not a linux user but see in https://lame.sourceforge.io/ , and ffmpeg work also in Linux (Debian, Ubuntu or Fedora pakages)] Last edited by tebasuna51; 26th September 2021 at 01:43.