参考以下帖子：
http://blog.csdn.net/vblittleboy/article/details/20121341作了一下改动，修正了bug，提高适用性：
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <libavutil/opt.h>
#include <libavutil/mathematics.h>
#include <libavformat/avformat.h>
FILE * fp_in = NULL;
FILE * fp_out = NULL;
static int frame_count;
int main(int argc, char **argv)
{
int ret;
AVCodec *audio_codec;
AVCodecContext *c;
AVFrame *frame;
AVPacket pkt = { 0 }; // data and size must be 0;
int got_output;
/* Initialize libavcodec, and register all codecs and formats. */
av_register_all();
avcodec_register_all();
//avdevice_register_all();
audio_codec = avcodec_find_encoder(AV_CODEC_ID_AAC);
c = avcodec_alloc_context3(audio_codec);
// c->strict_std_compliance =FF_COMPLIANCE_EXPERIMENTAL;
c->codec_id = AV_CODEC_ID_AAC;
c->sample_fmt = AV_SAMPLE_FMT_S16;
c->sample_rate = 44100;
c->channels = 2;
c->channel_layout = AV_CH_LAYOUT_STEREO;
c->bit_rate = 64000;
/* open the codec */
ret = avcodec_open2(c, audio_codec, NULL);
if (ret < 0) {
fprintf(stderr, "Could not open video codec: %s\n", av_err2str(ret));
exit(1);
}
/* allocate and init a re-usable frame */
#if 0
frame = avcodec_alloc_frame();
#else
frame = av_frame_alloc();
#endif
if (!frame) {
fprintf(stderr, "Could not allocate video frame\n");
exit(1);
}
frame->nb_samples = c->frame_size;
frame->format = c->sample_fmt;
frame->channels = c->channels;
frame->channel_layout = c->channel_layout;
#if 0
frame->linesize[0] = 4096;
frame->extended_data = frame->data[0] = av_malloc((size_t)frame->linesize[0]);
#else
ret = av_frame_get_buffer(frame, 0);
if (ret < 0) {
fprintf(stderr, "Could not allocate an audio frame.\n");
exit(1);
}
printf("----nb_samples= %d, linesize= %d\n", frame->nb_samples, frame->linesize[0]);
#endif
av_init_packet(&pkt);
fp_in = fopen("in.wav","rb");
fp_out= fopen("out.aac","wb");
//printf("frame->nb_samples = %d\n",frame->nb_samples);
while(1)
{
frame_count++;
bzero(frame->data[0],frame->linesize[0]);
ret = fread(frame->data[0],frame->linesize[0],1,fp_in);
if(ret <= 0)
{
printf("read over !\n");
break;
}
ret = avcodec_encode_audio2(c, &pkt, frame, &got_output);
if (ret < 0) {
fprintf(stderr, "Error encoding audio frame: %s\n", av_err2str(ret));
exit(1);
}
if(got_output > 0)
{
//printf("pkt.size = %d\n",pkt.size);
fwrite(pkt.data,pkt.size,1,fp_out);
av_free_packet(&pkt);
}
#if 0
if(frame_count > 10)
{
printf("break @@@@@@@@@@@@\n");
break;
}
#endif
}
avcodec_close(c);
av_free(c);
#if 0
avcodec_free_frame(&frame);
#else
av_frame_free(&frame);
#endif
fclose(fp_in);
fclose(fp_out);
return 0;
}
另外，建议看一下ffmpeg自带的例程，很有参考价值（特别是需要用到重采样功能）：
doc/examples/transcode_aac.c
注：
aac编码用到了libfdk_aac库，详细请参考：
http://trac.ffmpeg.org/wiki/Encode/AAC
posted on 2017-02-10 11:24
lfc 阅读(2017)
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