I decode an mp3 song using two different methods. The output PCM signals are shown in Figure 1 and Figure 2 respectively. Both the decoded output files have the same file size and audio quality. However, there exist some difference between the PCM signals. What causes the spike in PCM signal?
These spikes are high frequency components contained in the resulting signal decode. There are two possible reasons for this.
- Method one uses a low pass filter which removes these components.
- Method two has a decoding fault.
Both of these suggestions are speculative as there is no reference signal to compare.