h264.js

(function (root, factory) {
    if (typeof define === 'function' && define.amd) {
        // AMD. Register as an anonymous module.
        define(['jbinary'], factory);
    } else if (typeof exports === 'object') {
        // Node. Does not work with strict CommonJS, but
        // only CommonJS-like environments that support module.exports,
        // like Node.
        module.exports = factory(require('jbinary'));
    } else {
        // Browser globals (root is window)
        root.H264 = factory(root.jBinary);
    }
}(this, function (jBinary) {
	'use strict';

	return {
		ExpGolomb: jBinary.Type({
			params: ['isSigned'],
			read: function () {
				var count = 0;
				while (!this.binary.read(1)) count++;
				var value = (1 << count) | this.binary.read(count);
				return this.isSigned ? (value & 1 ? -(value >> 1) : value >> 1) : value - 1;
			},
			write: function (value) {
				if (this.isSigned) {
					value <<= 1;
					if (value <= 0) {
						value = -value | 1;
					}
				} else {
					value++;
				}
				var length = value.toString(2).length;
				this.binary.write(length - 1, 0);
				this.binary.write(length, value);
			}
		}),

		Optional: jBinary.Template({
		    params: ['baseType'],
			read: function () {
				if (this.binary.read(1)) return this.baseRead();
			},
			write: function (value) {
				this.binary.write(value != null ? 1 : 0);
				if (value != null) {
					this.baseWrite(value);
				}
			}
		}),

		ScalingList: jBinary.Template({
			setParams: function (size) {
				this.baseType = ['array', { /* TODO: implement scaling list */ }, size];
			}
		}),

		SPS: [
			'extend',
			{
				profile_idc: 'uint8',
				constraint_set_flags: ['array', 1, 8],
				level_idc: 'uint8',
				seq_parameter_set_id: 'ExpGolomb'
			},
			['if', function (context) { return [100, 110, 122, 244, 44, 83, 86, 118].indexOf(context.profile_idc) >= 0 }, {
				chroma_format: ['enum', 'ExpGolomb', ['MONO', 'YUV420', 'YUV422', 'YUV444']],
				separate_color_plane_flag: ['if', function (context) { return context.chroma_format === 'YUV444' }, 1],
				bit_depth_luma_minus8: 'ExpGolomb',
				bit_depth_chroma_minus8: 'ExpGolomb',
				qpprime_y_zero_transform_bypass_flag: 1,
				scaling_matrix: ['Optional', {
					scalingList4x4: ['array', ['ScalingList', 16], 6],
					scalingList8x8: ['array', ['ScalingList', 64], function () { return this.binary.getContext(1).chroma_format !== 'YUV444' ? 2 : 6 }]
				}]
			}],
			{
				log2_max_frame_num_minus4: 'ExpGolomb',
				pic_order_cnt_type: 'ExpGolomb',
				pic_order: ['if_not', 'pic_order_cnt_type', {log2_max_pic_order_cnt_lsb_minus4: 'ExpGolomb'}, [
					'if',
					function (context) { return context.pic_order_cnt_type === 1 },
					{
						delta_pic_order_always_zero_flag: 1,
						offset_for_non_ref_pic: ['ExpGolomb', true],
						offset_for_top_to_bottom_field: ['ExpGolomb', true],
						_num_ref_frames_in_pic_order_cnt_cycle: jBinary.Template({
							baseType: 'ExpGolomb',
							write: function (value, context) { this.baseWrite(context.offset_for_ref_frame.length) }
						}),
						offset_for_ref_frame: ['array', ['ExpGolomb', true], function (context) { return context._num_ref_frames_in_pic_order_cnt_cycle }]
					}
				]],
				max_num_ref_frames: 'ExpGolomb',
				gaps_in_frame_num_value_allowed_flag: 1,
				pic_width_in_mbs_minus_1: 'ExpGolomb',
				pic_height_in_map_units_minus_1: 'ExpGolomb',
				frame_mbs_only_flag: 1,
				mb_adaptive_frame_field_flag: ['if_not', 'frame_mbs_only_flag', 1],
				direct_8x8_inference_flag: 1,
				frame_cropping: ['Optional', {
					left: 'ExpGolomb',
					right: 'ExpGolomb',
					top: 'ExpGolomb',
					bottom: 'ExpGolomb'
				}]
				// TODO: add VUI parameters
			}
		],

		NALUnit: jBinary.Type({
			read: function () {
				var sync = this.binary.read(['blob', 3]); // [0, 0, 1] or [0, 0, 0, 1]
				if (sync[2] === 0) this.binary.skip(1);
				var end = this.binary.view.byteLength, pos = this.binary.tell();
				var bytes = this.binary.skip(0, function () { return this.view.getBytes() });
				for (var i = 1, length = bytes.length - 3; i < length; i++) {
					if (bytes[i] === 0 && bytes[i + 1] === 0 && (bytes[i + 2] === 1 || (bytes[i + 2] === 0 && bytes[i + 3] === 1))) {
						end = pos + i;
						break;
					}
				}
				var data = this.binary.read(['blob', end - pos]);
				// TODO: ideally there should be Annex.B conversion from [0, 0, 3, X=0..3] to [0, 0, X]
				return data;
			}
		})
	};
}));