H264 Decoder

Just an H264 decoder. That's all. Usable in the browser & node.

This project is based on the WebAssembly H264 decoder from TinyH264Decoder. Some unnecessary WASM functions have been stripped out, and the JS wrapper simplified. The WebAssembly module is inlined as a Base64-encoded string, so now special loading provisions are necessary. Just import { H264Decoder } from 'h264decoder'; and go. If you want to run it in a worker or a subprocess, that's up to you.

Create a new decoder with new H264Decoder();.

H264Decoder objects have a single public method: decoder.decode(nalu: Uint8Array): number. Input is expected in the form of single, complete, pre-segmented H264 Network Abstraction Layer Units (NALUs). Input is expected to be complete NALs (access units) as Uint8Array, the output result is a yuv420 buffer as Uint8Array. The return value is a number from the set

H264Decoder.RDY = 0;
H264Decoder.PIC_RDY = 1;
H264Decoder.HDRS_RDY = 2;
H264Decoder.ERROR = 3;
H264Decoder.PARAM_SET_ERROR = 4;
H264Decoder.MEMALLOC_ERROR = 5;

When decoder.decode(nalu) returns PIC_RDY, an output frame can be accessed through decoder.pic as a Uint8Array of YUV420 data. You are on your own for converting that to RGB if you like. The frame dimensions can be accessed through decoder.width and decoder.height. The array returned through decoder.pic aliases internal data structures to minimize unnecessary data copying--treat it as read-only and don't mess with it! If you need to do any further processing on the image, write to a separate buffer.

There are no cleanup or reset operations. If you are done decoding a particular stream, it is expected that you will simply discard the entire decoder and create a new one as needed.