[Firefox] Data from right channel is not passed to encoder despite there are expected two channels

[dominiksekula]

Hi! 👋
Firstly, thanks for your work on this project! 🙂

Today I used patch-package to patch lamejs@1.2.0 for the project I'm working on.

I encountered an issue in Firefox (v96.0.3) that variable for the right channel is not passed to the encodeBuffer despite there are 2 channels. To prevent that I've added extra validation of the presence of that right channel. That could probably simply replace checking for number of channels instead of extend that validation condition but I didn't investigate the code deeper and as a quick fix I went with the safest solution from my point of view.

Here is the diff that solved my problem:

diff --git a/node_modules/lamejs/src/js/index.js b/node_modules/lamejs/src/js/index.js
index 7539d66..f18e7c7 100644
--- a/node_modules/lamejs/src/js/index.js
+++ b/node_modules/lamejs/src/js/index.js
@@ -115,7 +115,8 @@ function Mp3Encoder(channels, samplerate, kbps) {
     var mp3buf = new_byte(mp3buf_size);
 
     this.encodeBuffer = function (left, right) {
-        if (channels == 1) {
+
+        if (channels == 1 || !right) {
             right = left;
         }
         assert(left.length == right.length);

This issue body was partially generated by patch-package.