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I am working on Arch Linux and am trying to create an intro movie for my Youtube channel. The idea is to play "intro.mp3" which is played only once and then "loop.mp3" which will be playing on low volume in the background for like ten minutes or so.

So in order to do this I took a "song.mp3" and checked it's metadata with mediainfo terminal command:

General
Complete name                            : song.mp3
Format                                   : MPEG Audio
File size                                : 2.78 MiB
Duration                                 : 1 min 12 s
Overall bit rate mode                    : Constant
Overall bit rate                         : 320 kb/s
Album                                    : Images And Words
Track name                               : Learning To Live
Track name/Position                      : 08
Performer                                : Dream Theater
Genre                                    : Progressive Metal
Recorded date                            : 1992
Writing library                          : LAME3.98r
FMPS_Rating                              : 1
FMPS_Playcount                           : 3
FMPS_Rating_Amarok_Score                 : 0.5325

Audio
Format                                   : MPEG Audio
Format version                           : Version 1
Format profile                           : Layer 3
Mode                                     : Joint stereo
Duration                                 : 1 min 12 s
Bit rate mode                            : Constant
Bit rate                                 : 320 kb/s
Channel(s)                               : 2 channels
Sampling rate                            : 44.1 kHz
Compression mode                         : Lossy
Stream size                              : 2.78 MiB (100%)
Writing library                          : LAME3.98r
Encoding settings                        : -m m -V 10 -q 0

After this I started JACK audio server with settings set like this (note the sample rate 44100 is the same as for the "song.mp3"):

enter image description here enter image description here

And then Bitwig studio which I used to split the "song.mp3" into two separate files "intro.wav" and "loop-x5.wav" (Bitwig only exports in wav) and in 32 bit depth:

enter image description here

Now if I check media details with mediainfo terminal command I get:

General
Complete name                            : loop-x5.wav
Format                                   : Wave
File size                                : 13.8 MiB
Duration                                 : 40 s 909 ms
Overall bit rate mode                    : Constant
Overall bit rate                         : 2 822 kb/s

Audio
Format                                   : PCM
Format profile                           : Float
Codec ID                                 : 3
Codec ID/Hint                            : IEEE 
Duration                                 : 40 s 909 ms
Bit rate mode                            : Constant
Bit rate                                 : 2 822 kb/s
Channel(s)                               : 2 channels
Sampling rate                            : 44.1 kHz
Bit depth                                : 32 bits
Stream size                              : 13.8 MiB (100%)

and

General                                                                                                                                 
Complete name                            : intro.wav                                                                                    
Format                                   : Wave                                                                                         
File size                                : 5.52 MiB                                                                                     
Duration                                 : 16 s 397 ms                                                                                  
Overall bit rate mode                    : Constant                                                                                     
Overall bit rate                         : 2 823 kb/s                                                                                   

Audio                                                                                                                                   
Format                                   : PCM                                                                                          
Format profile                           : Float                                                                                        
Codec ID                                 : 3                                                                                            
Codec ID/Hint                            : IEEE                                                                                         
Duration                                 : 16 s 397 ms                                                                                  
Bit rate mode                            : Constant                                                                                     
Bit rate                                 : 2 822 kb/s
Channel(s)                               : 2 channels
Sampling rate                            : 44.1 kHz
Bit depth                                : 32 bits
Stream size                              : 5.52 MiB (100%)

Which looks completely fine to me and if I import these files back into Bitwig files are played at the same speed. Things change if I use FFMPEG to convert files into mp3 format like this:

ffmpeg -i intro.wav -vn -ar 44100 -ac 2 -ab 192 -f mp3 intro.mp3
ffmpeg -i loop-x5.wav -vn -ar 44100 -ac 2 -ab 192 -f mp3 loop-x5.mp3

Now if I import mp3 files back into Bitwig they are out of sync. One plays faster than the other. Why? Here is also the info about mp3 files:

General
Complete name                            : intro.mp3
Format                                   : MPEG Audio
File size                                : 257 KiB
Overall bit rate mode                    : Variable
Writing library                          : Lavf57.41.100

Audio
Format                                   : MPEG Audio
Format version                           : Version 1
Format profile                           : Layer 3
Mode                                     : Joint stereo
Mode extension                           : MS Stereo
Bit rate mode                            : Variable
Channel(s)                               : 2 channels
Sampling rate                            : 44.1 kHz
Compression mode                         : Lossy
Stream size                              : 257 KiB (100%)

and

General
Complete name                            : loop-x5.mp3
Format                                   : MPEG Audio
File size                                : 640 KiB
Overall bit rate mode                    : Variable
Writing library                          : Lavf57.41.100

Audio
Format                                   : MPEG Audio
Format version                           : Version 1
Format profile                           : Layer 3
Mode                                     : Joint stereo
Mode extension                           : MS Stereo
Bit rate mode                            : Variable
Channel(s)                               : 2 channels
Sampling rate                            : 44.1 kHz
Compression mode                         : Lossy
Stream size                              : 640 KiB (100%)
1

Have you tried exporting the .wavs from Bitwig as 24-bit? It may be that for some reason the the 32 bit-depth(float) upsets the FFMPEG conversion.

  • I did try to export using Bitwig in 32-bit and 24-bit and in either cases I am getting out-of-sync audios... – 71GA Sep 18 '16 at 10:12

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