4 ms·

As a wise Keanu Reeves once said, "Woah." Is there any upper limit you've found with bitrates, etc.? Also, what was the most difficult part in building this?

jensnockert 15y ago
320kBit ones works fine (the max for MPEG1/2 streams.) We did most of the work during and after Music Hackday Berlin (and it was continued at MHD Barcelona) and just staying awake was quite difficult, but porting much of the low-level bitfiddling and pointer-stuff to javascript was hard because of language differences, but also converting a fixed-point library to the floating-point that is available in javascript was a bit of trouble.
nddrylliog 15y ago
Been playing 320kbps Stereo flawlessly afaik. The bitrate is really not much of an issue. Browsers have a much harder time dealing with binary XHRs, huge typed arrays, huge strings, and a real fucking lot of arithmetic operations. I think the most difficult part was the debugging. Jens Nockert, Matthias Georgi & I finally used node.js and carefully diff'd the output from minimad.c (the canonical libmad example) and jsmad. However, it quickly became obvious that comparing exact values wasn't going to cut it. Listening was also almost useless (try to debug when all you have is SCRRRCHHHHHH vs CRRRRRRKKKKKK). So we plotted graphs. With gnuplot. It was a matrix-like experience but quickly allowed us to see what was wrong. Profiling the code via Firebug made us realize that most of the time (~28%) was spent in the synthetizer (synth.js). The I/O code is particularly expensive too, it's a mix of Uint8Arrays and javascript Strings, depending on whether you're using the local file version (filestream.js) or the http streaming version (ajaxstream.js) One of the funniest part was when I had to code 36-bit precision integer routines in Javascript such as shifting, OR-ing, AND-ing.. I had to separate the numbers in a low word and a high word and then work with floats (which have a 54-bit mantissa in JS). Really quite an experience!
- jensnockert 15y ago
  *52 Bit. And I agree, debugging it was a special experience.
- halostatue 15y ago
  I suspect that there's a fairly interesting blog post with samples of the gnuplot output waiting to be written about this.
  - nddrylliog 15y ago
    That's a good idea. I think some of the graphs are still on the depo (in experiments/node/ or something).

jensnockert 15y ago

320kBit ones works fine (the max for MPEG1/2 streams.) We did most of the work during and after Music Hackday Berlin (and it was continued at MHD Barcelona) and just staying awake was quite difficult, but porting much of the low-level bitfiddling and pointer-stuff to javascript was hard because of language differences, but also converting a fixed-point library to the floating-point that is available in javascript was a bit of trouble.

nddrylliog 15y ago

Been playing 320kbps Stereo flawlessly afaik. The bitrate is really not much of an issue. Browsers have a much harder time dealing with binary XHRs, huge typed arrays, huge strings, and a real fucking lot of arithmetic operations. I think the most difficult part was the debugging. Jens Nockert, Matthias Georgi & I finally used node.js and carefully diff'd the output from minimad.c (the canonical libmad example) and jsmad. However, it quickly became obvious that comparing exact values wasn't going to cut it. Listening was also almost useless (try to debug when all you have is SCRRRCHHHHHH vs CRRRRRRKKKKKK). So we plotted graphs. With gnuplot. It was a matrix-like experience but quickly allowed us to see what was wrong. Profiling the code via Firebug made us realize that most of the time (~28%) was spent in the synthetizer (synth.js). The I/O code is particularly expensive too, it's a mix of Uint8Arrays and javascript Strings, depending on whether you're using the local file version (filestream.js) or the http streaming version (ajaxstream.js) One of the funniest part was when I had to code 36-bit precision integer routines in Javascript such as shifting, OR-ing, AND-ing.. I had to separate the numbers in a low word and a high word and then work with floats (which have a 54-bit mantissa in JS). Really quite an experience!

jensnockert 15y ago
*52 Bit. And I agree, debugging it was a special experience.
halostatue 15y ago
I suspect that there's a fairly interesting blog post with samples of the gnuplot output waiting to be written about this.
- nddrylliog 15y ago
  That's a good idea. I think some of the graphs are still on the depo (in experiments/node/ or something).