OpenH264-js

This is an example of the Cisco's OpenH264 library compiled to javascript with emscripten for running natively in browsers.

This is very similar to eg https://github.com/mbebenita/Broadway and others. The main difference is that they use the BSD decoder which is limited to h264 baseline profile. Among others, that means no cabac. OpenH264 (http://www.openh264.org/) does support cabac.

Features

• CABAC decoding
• Tested in Chrome v43 and Firefox 40
• single nal decoding, makes it easy to decode any container externally
• > 30 fps for 1280x720 main profile stream (cabac encoded) on Haswell i7

Limitiations

• Lot's of hardcoding in demo (decode.html).

Build instructions

• only tested on linux / emcc (Emscripten GCC-like replacement) 1.29.0 (commit fdf24b478e1b26c0362a1627aca49ef82fd53f6a)

• Get emscripten (http://kripken.github.io/emscripten-site/docs/getting_started/Tutorial.html)

• Run make

The Makefile will download all dependencies and build everything. A small demo is provided in decoder.html. The demo uses Broadway's rendering library.

Possible improvements

There are a lot of copying going on, Several reasons:

• A quick look didn't reveal any buffer control in OpenH264 (validity of data pointers are until next decode call?)
• Broadway's yuv->rgb conversion needs back-to-back planes with stride = width: OpenH264 doesn't do that.

Other points

• closure-compiler, even with at whitespace level makes playback slower and more jittery. No clue why.