UnderflowError when seeking

[kethinov]

I'm trying to make a very simple SPC player demo. Whenever I try to seek the SPC file, I get:

UnderflowError {name: 'AV.UnderflowError'}
AV.Stream.Stream.advance	@	spc-aurora.js:291
AV.Stream.Stream.seek	@	spc-aurora.js:321
AV.Decoder.Decoder.seek	@	spc-aurora.js:1265
AV.Player.Player.seek	@	spc-aurora.js:1765
(anonymous)	@	(index):88

You can see the bug here: https://kethinov.github.io/spc-playback-demo/

The full source code for my SPC demo which reproduces the bug is here: https://github.com/kethinov/spc-playback-demo

I've been banging my head debugging this for quite a while and all I've learned is the problem traces to these two functions from Aurora:

Stream.prototype.available = function(bytes) {
  return bytes <= this.list.availableBytes - this.localOffset;
};

And:

Stream.prototype.advance = function(bytes) {
  if (!this.available(bytes)) {
    throw new AV.UnderflowError();
  }
  this.localOffset += bytes;
  this.offset += bytes;
  while (this.list.first && this.localOffset >= this.list.first.length) {
    this.localOffset -= this.list.first.length;
    this.list.advance();
  }
  return this;
};

Specifically what's happening is when I seek forward, advance calls available. When available returns false, advance throws the UnderflowError. The reason available is returning false is this.localOffset is always 0. When I play other file formats in Aurora, this.localOffset is not 0 when seeking. This is making me wonder if there is a bug in spc.js that is causing this, but I have been unable to trace the problem any deeper to understand what is at the root of it.

Can anyone here help me get seeking working in my demo?

[MatthewCallis]

Hello! I didn't build spc.js up with seeking in mind as it is being simply rendered in to tiny chunks of WAVE and output directly in real time. Seeking will not work without a substantial reworking, and the reworking I am slowly doing is moving away from Aurora all together. So unfortunately I cannot help you here.

What you could possibly do is update the SPC.js library to support streaming the SPC file data, or rendering the entire thing to something that can be advanced rather than attempting to stream in real time.