Plot PCM output in Matlab (MP3 decoder)

Question

I am doing a mp3 decoder project and I have built a function to decode a song in mp3 format:

function [PCM_output,frequency] = decode(mp3song)

At the end of the code, I am adding a few lines to plot the PCM waveform:

t=0:0.01:120; 
plot(t,PCM_output);
title('PCM waveform');

But it shows error:

Vectors must be the same lengths.

How to solve the error? Besides, is it possible to output the decoded song in PCM format?

Additional Question: I want to compare the mp3 and PCM output as shown in the Figures below: MP3 - Amplitude vs Time

Why does the PCM has two output overlay together? Is it because of the left and right channel at the output?

Typing `length(t)` and `length(`PCM_output(1,:))` might help troubleshooting — brainkz, Jan 29 '16 at 04:34
I don't think there is a PCM format for audio file, but you can just `wavwrite` it and try to hear it. — GameOfThrows, Jan 29 '16 at 09:53
@brainkz, the `length(PCM_output(1,:))` is 9861120 while the time taken to decode is 10094s. Is it possible to plot the two variables in a graph? — Ralph, Feb 02 '16 at 03:36

score 0 · Accepted Answer · answered Feb 02 '16 at 05:57

0

If you try to plot your sound wave, you just need your t vector to be the same length as your PCM_output. So, instead of t=0:0.01:120 you need

t=linspace(0,120,length(PCM_output(1,:)));

answered Feb 02 '16 at 05:57

brainkz

1 Answers1