Add a decoding example that uses libavformat to demux .m4a files

Makefile.am

@@ -43,6 +43,14 @@ aac_dec_LDADD = libfdk-aac.la
 aac_dec_SOURCES = aac-dec.c wavwriter.c
 
 noinst_HEADERS = wavreader.h wavwriter.h
+
+if HAVE_LIBAVFORMAT
+bin_PROGRAMS += m4a-dec$(EXEEXT)
+
+m4a_dec_LDADD = $(libavformat_LIBS) libfdk-aac.la
+m4a_dec_CFLAGS = $(libavformat_CFLAGS)
+m4a_dec_SOURCES = m4a-dec.c wavwriter.c
+endif
 endif
 
 AACDEC_SRC = \

configure.ac

@@ -13,8 +13,13 @@ AC_ARG_ENABLE([example],
                 [enable example encoding program (default is no)])],
             [example=$enableval], [example=no])
 
+if test x$example = xyes; then
+	PKG_CHECK_MODULES([libavformat], [libavformat], [libavformat=yes], [libavformat=no])
+fi
+
 dnl Automake conditionals to set
 AM_CONDITIONAL(EXAMPLE, test x$example = xyes)
+AM_CONDITIONAL(HAVE_LIBAVFORMAT, test x$libavformat = xyes)
 
 dnl Checks for programs.
 AC_PROG_CC
@@ -36,3 +41,7 @@ AC_SUBST(LIBS_PRIVATE)
 AC_CONFIG_FILES([Makefile
                  fdk-aac.pc])
 AC_OUTPUT
+
+if test x$example = xyes; then
+	AC_MSG_NOTICE([Found libavformat: ${libavformat}])
+fi

m4a-dec.c

@@ -0,0 +1,139 @@
+/* ------------------------------------------------------------------
+ * Copyright (C) 2013 Martin Storsjo
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *	  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ * -------------------------------------------------------------------
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include "libAACdec/include/aacdecoder_lib.h"
+#include "wavwriter.h"
+#include <libavformat/avformat.h>
+
+#if LIBAVCODEC_VERSION_MAJOR < 55
+#define AV_CODEC_ID_AAC CODEC_ID_AAC
+#endif
+
+int main(int argc, char *argv[]) {
+	const char *infile, *outfile;
+	AVFormatContext *in = NULL;
+	AVStream *st = NULL;
+	void *wav = NULL;
+	int output_size, ret, i;
+	uint8_t *output_buf;
+	int16_t *decode_buf;
+	HANDLE_AACDECODER handle;
+	AAC_DECODER_ERROR err;
+	int frame_size = 0;
+	if (argc < 3) {
+		fprintf(stderr, "%s in.m4a out.wav\n", argv[0]);
+		return 1;
+	}
+	infile = argv[1];
+	outfile = argv[2];
+
+	av_register_all();
+	avformat_network_init();
+	ret = avformat_open_input(&in, infile, NULL, NULL);
+	if (ret < 0) {
+		char buf[100];
+		av_strerror(ret, buf, sizeof(buf));
+		fprintf(stderr, "%s: %s\n", infile, buf);
+		return 1;
+	}
+	for (i = 0; i < in->nb_streams && !st; i++) {
+		if (in->streams[i]->codec->codec_id == AV_CODEC_ID_AAC)
+			st = in->streams[i];
+	}
+	if (!st) {
+		fprintf(stderr, "No AAC stream found\n");
+		return 1;
+	}
+	if (!st->codec->extradata_size) {
+		fprintf(stderr, "No AAC ASC found\n");
+		return 1;
+	}
+	handle = aacDecoder_Open(TT_MP4_RAW, 1);
+	err = aacDecoder_ConfigRaw(handle, &st->codec->extradata, &st->codec->extradata_size);
+	if (err != AAC_DEC_OK) {
+		fprintf(stderr, "Unable to decode the ASC\n");
+		return 1;
+	}
+
+	output_size = 8*2*1024;
+	output_buf = (uint8_t*) malloc(output_size);
+	decode_buf = (int16_t*) malloc(output_size);
+
+	while (1) {
+		int i;
+		UINT valid;
+		AVPacket pkt = { 0 };
+		int ret = av_read_frame(in, &pkt);
+		if (ret < 0) {
+			if (ret == AVERROR(EAGAIN))
+				continue;
+			break;
+		}
+		if (pkt.stream_index != st->index) {
+			av_free_packet(&pkt);
+			continue;
+		}
+
+		valid = pkt.size;
+		err = aacDecoder_Fill(handle, &pkt.data, &pkt.size, &valid);
+		if (err != AAC_DEC_OK) {
+			fprintf(stderr, "Fill failed: %x\n", err);
+			break;
+		}
+		err = aacDecoder_DecodeFrame(handle, decode_buf, output_size, 0);
+		av_free_packet(&pkt);
+		if (err == AAC_DEC_NOT_ENOUGH_BITS)
+			continue;
+		if (err != AAC_DEC_OK) {
+			fprintf(stderr, "Decode failed: %x\n", err);
+			continue;
+		}
+		if (!wav) {
+			CStreamInfo *info = aacDecoder_GetStreamInfo(handle);
+			if (!info || info->sampleRate <= 0) {
+				fprintf(stderr, "No stream info\n");
+				break;
+			}
+			frame_size = info->frameSize * info->numChannels;
+			// Note, this probably doesn't return channels > 2 in the right order for wav
+			wav = wav_write_open(outfile, info->sampleRate, 16, info->numChannels);
+			if (!wav) {
+				perror(outfile);
+				break;
+			}
+		}
+		for (i = 0; i < frame_size; i++) {
+			uint8_t* out = &output_buf[2*i];
+			out[0] = decode_buf[i] & 0xff;
+			out[1] = decode_buf[i] >> 8;
+		}
+		wav_write_data(wav, output_buf, 2*frame_size);
+	}
+	free(output_buf);
+	free(decode_buf);
+	avformat_close_input(&in);
+	if (wav)
+		wav_write_close(wav);
+	aacDecoder_Close(handle);
+	return 0;
+}
+