/*
 * LATM/LOAS muxer
 * Copyright (c) 2011 Kieran Kunhya <kieran@kunhya.com>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/* ***************************** */
/* Includes                      */
/* ***************************** */
#include <ffmpeg/get_bits.h>
#include <ffmpeg/put_bits.h>
#include <ffmpeg/mpeg4audio.h>
#include <ffmpeg/latmenc.h>
#include "debug.h"

/* ***************************** */
/* Makros/Constants              */
/* ***************************** */

int latmenc_decode_extradata(LATMContext *ctx, uint8_t *buf, int size)
{
	MPEG4AudioConfig m4ac;

	if (size > MAX_EXTRADATA_SIZE)
	{
		latmenc_err("Extradata is larger than currently supported.\n");
		return AVERROR_INVALIDDATA;
	}
	ctx->off = avpriv_mpeg4audio_get_config(&m4ac, buf, size * 8, 1);
	if (ctx->off < 0)
		return ctx->off;

	if (ctx->object_type == AOT_ALS && (ctx->off & 7))
	{
		// as long as avpriv_mpeg4audio_get_config works correctly this is impossible
		latmenc_err("BUG: ALS offset is not byte-aligned\n");
		return AVERROR_INVALIDDATA;
	}
	/* FIXME: are any formats not allowed in LATM? */

	if (m4ac.object_type > AOT_SBR && m4ac.object_type != AOT_ALS)
	{
		latmenc_err("Muxing MPEG-4 AOT %d in LATM is not supported\n", m4ac.object_type);
		return AVERROR_INVALIDDATA;
	}
	ctx->channel_conf = m4ac.chan_config;
	ctx->object_type  = m4ac.object_type;

	return 0;
}

static void latmenc_write_frame_header(LATMContext *ctx, uint8_t *extradata, int extradata_size, PutBitContext *bs)
{
	int header_size;

	/* AudioMuxElement */
	put_bits(bs, 1, !!ctx->counter);

	if (!ctx->counter)
	{
		/* StreamMuxConfig */
		put_bits(bs, 1, 0); /* audioMuxVersion */
		put_bits(bs, 1, 1); /* allStreamsSameTimeFraming */
		put_bits(bs, 6, 0); /* numSubFrames */
		put_bits(bs, 4, 0); /* numProgram */
		put_bits(bs, 3, 0); /* numLayer */

		/* AudioSpecificConfig */
		if (ctx->object_type == AOT_ALS)
		{
			header_size = extradata_size - (ctx->off >> 3);
			avpriv_copy_bits(bs, &extradata[ctx->off >> 3], header_size);
		}
		else
		{
			// + 3 assumes not scalable and dependsOnCoreCoder == 0,
			// see decode_ga_specific_config in libavcodec/aacdec.c
			avpriv_copy_bits(bs, extradata, ctx->off + 3);

			if (!ctx->channel_conf)
			{
				GetBitContext gb;
				int ret = init_get_bits8(&gb, extradata, extradata_size);
				av_assert0(ret >= 0); // extradata size has been checked already, so this should not fail
				skip_bits_long(&gb, ctx->off + 3);
				avpriv_copy_pce_data(bs, &gb);
			}
		}

		put_bits(bs, 3, 0); /* frameLengthType */
		put_bits(bs, 8, 0xff); /* latmBufferFullness */

		put_bits(bs, 1, 0); /* otherDataPresent */
		put_bits(bs, 1, 0); /* crcCheckPresent */
	}

	ctx->counter++;
	ctx->counter %= ctx->mod;
}

int latmenc_write_packet(LATMContext *ctx, uint8_t *data, int size, uint8_t *extradata, int extradata_size)
{
	PutBitContext bs;
	int i, len;

	if (size > 0x1fff)
		goto too_large;

	init_put_bits(&bs, ctx->buffer, size + 1024 + MAX_EXTRADATA_SIZE);

	latmenc_write_frame_header(ctx, extradata, extradata_size, &bs);

	/* PayloadLengthInfo() */
	for (i = 0; i <= size - 255; i += 255)
		put_bits(&bs, 8, 255);

	put_bits(&bs, 8, size - i);

	/* The LATM payload is written unaligned */

	/* PayloadMux() */
	if (size && (data[0] & 0xe1) == 0x81)
	{
		// Convert byte-aligned DSE to non-aligned.
		// Due to the input format encoding we know that
		// it is naturally byte-aligned in the input stream,
		// so there are no padding bits to account for.
		// To avoid having to add padding bits and rearrange
		// the whole stream we just remove the byte-align flag.
		// This allows us to remux our FATE AAC samples into latm
		// files that are still playable with minimal effort.
		put_bits(&bs, 8, data[0] & 0xfe);
		avpriv_copy_bits(&bs, data + 1, 8 * size - 8);
	}
	else
		avpriv_copy_bits(&bs, data, 8 * size);

	avpriv_align_put_bits(&bs);
	flush_put_bits(&bs);

	len = put_bits_count(&bs) >> 3;

	if (len > 0x1fff)
		goto too_large;

	memcpy(ctx->loas_header, "\x56\xe0\x00", 3);
	ctx->loas_header[1] |= (len >> 8) & 0x1f;
	ctx->loas_header[2] |= len & 0xff;
	ctx->len = len;
	return 0;

too_large:
	latmenc_err("LATM packet size larger than maximum size 0x1fff\n");
	return AVERROR_INVALIDDATA;
}