Vorbis - Feb 2013 - Vorbis encoding using JavaScript

Hello,

First of all, I am a complete newblet to anything dealing with audio (a lot
of the vocabulary is still rather mysterious to me). I also don't often
program in C so please don't throw too many stones if my workflow is less
than ideal. :)

I would like to port the vorbis encoder to JavaScript. Instead of porting
everything by hand from ground up, which would take who-knows-how-long, I
am using a tool called emscripten (https://github.com/kripken/emscripten).

>________________________________
> From: Mateusz Wielgos <wielgosm at gmail.com>
>To: vorbis at xiph.org 
>Sent: Wednesday, February 13, 2013 7:41 AM
>Subject: [Vorbis] Vorbis encoding using JavaScript
> 
>
>Hello,
>
>
>First of all, I am a complete newblet to anything dealing with audio (a lot
of the vocabulary is still rather mysterious to me). I also don't often
program in C so please don't throw too many stones if my workflow is less
than ideal. :)
>
>
>I would like to port the vorbis encoder to JavaScript. Instead of porting
everything by hand from ground up, which would take who-knows-how-long, I am
using a tool called emscripten (https://github.com/kripken/emscripten). From the
docs:
>
>
>Emscripten is an LLVM-to-JavaScript compiler. It takes LLVM bitcode - which
can be generated from C/C++, using llvm-gcc or clang, or any other language that
can be converted into LLVM - and compiles that into JavaScript, which can be run
on the web (or anywhere else JavaScript can run).
>
>
>I was able to successfully build libogg, libvorbis and libvorbis examples
using this tool and generate valid JavaScript (hopefully working as intended
also...).
>
>
>In JavaScript, once I obtain the left and right channel audio data (using
W3C web audio api) I pass this data into the JavaScript encoder as command line
arguments. This data is then read, each string converted to a float, and the
vorbis_analysis_buffer is filled with this "parsed" data. Similarly, I
pass the quality as an argument and run vorbis_encode_init_vbr accordingly.
>
>
>One last thing that I pass in is a "state" of a stream - either
the beginning, middle, or end so I can handle these cases differently (for
example, at the start of the stream I set all necessary headers).
>
>
>The generated file, however, does not seem to be valid and does not play.
>
>
>Could somebody verify that my encoding logic is sound? Here is the C source
on GitHub (based on libvorbis encoder_example.c)
:?https://github.com/mateusz-/vorbisenc.js/blob/master/encoder_example.c
>And, if it helps, here is the corrupted/invalid Ogg file
:?https://raw.github.com/mateusz-/vorbisenc.js/master/audio.ogg
>
>
>Thank you,
>Mateusz
>_______________________________________________
>Vorbis mailing list
>Vorbis at xiph.org
>http://lists.xiph.org/mailman/listinfo/vorbis
>
>
>
I am just a user of Ogg/Vorbis, so I can't answer your questions
specifically.

Still, have you tested everything in "C" ? I.e. does your
https://github.com/mateusz-/vorbisenc.js/blob/master/encoder_example.c work as
expected ?

Because if it doesn't, JavaScript has nothing to do with your problem.

Regards,
? Sergei.

> The generated file, however, does not seem to be valid and does not play.
>
> Could somebody verify that my encoding logic is sound? Here is the C source
> on GitHub (based on libvorbis encoder_example.c) :
> https://github.com/mateusz-/vorbisenc.js/blob/master/encoder_example.c
> And, if it helps, here is the corrupted/invalid Ogg file :
> https://raw.github.com/mateusz-/vorbisenc.js/master/audio.ogg
Looking at the file itself, the Ogg encapsulation is there but the
page checksums are all incorrect.  There are checksums present, just
incorrect, so the checksum generation code would be the first to
verify.

Monty