FFMPEG AAC encoder issue - audio

Question

I am trying to capture and encode audio data, I am encoding audio using
FFMPEG AAC and to capture PCM data I used ALSA, Capturing part is working in my case, However, AAC encoder is not working.
I am trying to play test.aac file using
ffplay test.aac
but it contains lots of noise.
Attaching code for aac encoder :
#include "AudioEncoder.h"
void* AudioEncoder::run(void *ctx)
{
return ((AudioEncoder *)ctx)->execute();
}
static int frameCount = 0;
void* AudioEncoder::execute(void)
{
float buf[size], *temp;
int totalSize = 0;
int fd = open("in.pcm", O_CREAT| O_RDWR, 0666);
int frameSize = 128 * snd_pcm_format_width(SND_PCM_FORMAT_FLOAT) / 8 * 2;
av_new_packet(&pkt,size);
cout << size << endl;
while (!Main::stopThread)
{
temp = (Main::fbAudio)->dequeue();
memcpy(buf + totalSize, temp, frameSize);
write(fd, temp, frameSize); // Can play in.pcm with no noise in it.
totalSize += frameSize;
delete temp;
if (totalSize >= size)
{
totalSize = 0;
//frame_buf = (uint8_t *) buf;
pFrame->data[0] = (uint8_t *)buf; //PCM Data
pFrame->pts=frameCount;
frameCount++;
got_frame=0;
//Encode
ret = avcodec_encode_audio2(pCodecCtx, &pkt,pFrame, &got_frame);
if(ret < 0){
cerr << "Failed to encode!\n";
return NULL;
}
if (got_frame==1){
printf("Succeed to encode 1 frame! \tsize:%5d\n",pkt.size);
pkt.stream_index = audio_st->index;
#ifdef DUMP_TEST
ret = av_write_frame(pFormatCtx, &pkt);
#endif
av_free_packet(&pkt);
}
//memset(buf, 0, sizeof(float)*size);
}
//delete temp;
//if (buf.size() >= m_audio_output_decoder_ctx->frame_size)
/* encode the audio*/
}
close(fd);
Main::stopThread = true;
return NULL;
}
int AudioEncoder::flush_encoder(AVFormatContext *fmt_ctx,unsigned int stream_index){
int ret;
int got_frame;
AVPacket enc_pkt;
if (!(fmt_ctx->streams[stream_index]->codec->codec->capabilities &
CODEC_CAP_DELAY))
return 0;
while (1) {
enc_pkt.data = NULL;
enc_pkt.size = 0;
av_init_packet(&enc_pkt);
ret = avcodec_encode_audio2 (fmt_ctx->streams[stream_index]->codec, &enc_pkt,
NULL, &got_frame);
av_frame_free(NULL);
if (ret < 0)
break;
if (!got_frame){
ret=0;
break;
}
printf("Flush Encoder: Succeed to encode 1 frame!\tsize:%5d\n",enc_pkt.size);
/* mux encoded frame */
#ifdef DUMP_TEST
ret = av_write_frame(fmt_ctx, &enc_pkt);
if (ret < 0)
break;
#endif
}
return ret;
}
void AudioEncoder::start(void)
{
pthread_t encoder;
pthread_create(&encoder, NULL, &AudioEncoder::run, this);
}
AudioEncoder::AudioEncoder() : out_file("test.aac")
{
got_frame = 0;
ret = 0;
size = 0;
av_register_all();
avcodec_register_all();
//Method 1.
pFormatCtx = avformat_alloc_context();
fmt = av_guess_format(NULL, out_file, NULL);
pFormatCtx->oformat = fmt;
#ifdef DUMP_TEST
if (avio_open(&pFormatCtx->pb,out_file, AVIO_FLAG_READ_WRITE) < 0){
cerr << "Failed to open output file!\n";
return;
}
#endif
audio_st = avformat_new_stream(pFormatCtx, 0);
if (audio_st==NULL){
return;
}
pCodecCtx = audio_st->codec;
pCodecCtx->codec_id = fmt->audio_codec;
pCodecCtx->codec_type = AVMEDIA_TYPE_AUDIO;
pCodecCtx->sample_fmt = AV_SAMPLE_FMT_FLTP;
pCodecCtx->sample_rate= 8000;
pCodecCtx->channel_layout=AV_CH_LAYOUT_STEREO;
pCodecCtx->channels = av_get_channel_layout_nb_channels(pCodecCtx->channel_layout);
// pCodecCtx->bit_rate = 64000;
#ifdef DUMP_TEST
//Show some information
av_dump_format(pFormatCtx, 0, out_file, 1);
#endif
pCodec = avcodec_find_encoder(pCodecCtx->codec_id);
if (!pCodec){
printf("Can not find encoder!\n");
return;
}
if (avcodec_open2(pCodecCtx, pCodec,NULL) < 0){
printf("Failed to open encoder!\n");
return;
}
pFrame = av_frame_alloc();
pFrame->nb_samples= pCodecCtx->frame_size;
pFrame->format= pCodecCtx->sample_fmt;
size = av_samples_get_buffer_size(NULL, pCodecCtx->channels,pCodecCtx->frame_size,pCodecCtx->sample_fmt, 1);
frame_buf = (uint8_t *)av_malloc(size);
avcodec_fill_audio_frame(pFrame, pCodecCtx->channels, pCodecCtx->sample_fmt,(const uint8_t*)frame_buf, size, 1);
//Write Header
#ifdef DUMP_TEST
avformat_write_header(pFormatCtx,NULL);
#endif
}
AudioEncoder::~AudioEncoder()
{
//Flush Encoder
ret = flush_encoder(pFormatCtx,0);
if (ret < 0) {
cerr << "Flushing encoder failed\n";
return;
}
#ifdef DUMP_TEST
//Write Trailer
av_write_trailer(pFormatCtx);
#endif
//Clean
if (audio_st){
avcodec_close(audio_st->codec);
av_free(pFrame);
av_free(frame_buf);
}
avio_close(pFormatCtx->pb);
avformat_free_context(pFormatCtx);
}
Here, please ignore DUMP_TEST flag, I already enabled it.
Can some one tell me what is issue ?
Thanks,
Harshil

Answer 1

I am able to resolve this issue, by correctly passing buffer from ALSA to AAC encoder.
Here AAC expects buffer size of 4096 bytes, but from deque I am passing 1024 bytes which causes issue, also I updated audio channels to MONO, in place of STEREO. Attaching my working code snippet for more information:
#include "AudioEncoder.h"
void* AudioEncoder::run(void *ctx)
{
return ((AudioEncoder *)ctx)->execute();
}
static int frameCount = 0;
void* AudioEncoder::execute(void)
{
float *temp;
#ifdef DUMP_TEST
int fd = open("in.pcm", O_CREAT| O_RDWR, 0666);
#endif
int frameSize = 1024 * snd_pcm_format_width(SND_PCM_FORMAT_FLOAT) / 8 * 1;
av_new_packet(&pkt,size);
while (!Main::stopThread)
{
temp = (Main::fbAudio)->dequeue();
frame_buf = (uint8_t *) temp;
pFrame->data[0] = frame_buf;
pFrame->pts=frameCount*100;
frameCount++;
got_frame=0;
//Encode
ret = avcodec_encode_audio2(pCodecCtx, &pkt,pFrame, &got_frame);
if(ret < 0){
cerr << "Failed to encode!\n";
return NULL;
}
if (got_frame==1){
cout << "Encoded frame\n";
pkt.stream_index = audio_st->index;
#ifdef DUMP_TEST
write(fd, temp, frameSize);
ret = av_interleaved_write_frame(pFormatCtx, &pkt);
#endif
av_free_packet(&pkt);
}
delete temp;
}
#ifdef DUMP_TEST
close(fd);
#endif
Main::stopThread = true;
return NULL;
}
int AudioEncoder::flush_encoder(AVFormatContext *fmt_ctx,unsigned int stream_index){
int ret;
int got_frame;
AVPacket enc_pkt;
if (!(fmt_ctx->streams[stream_index]->codec->codec->capabilities &
CODEC_CAP_DELAY))
return 0;
while (1) {
enc_pkt.data = NULL;
enc_pkt.size = 0;
av_init_packet(&enc_pkt);
ret = avcodec_encode_audio2 (fmt_ctx->streams[stream_index]->codec, &enc_pkt,
NULL, &got_frame);
av_frame_free(NULL);
if (ret < 0)
break;
if (!got_frame){
ret=0;
break;
}
printf("Flush Encoder: Succeed to encode 1 frame!\tsize:%5d\n",enc_pkt.size);
/* mux encoded frame */
#ifdef DUMP_TEST
ret = av_write_frame(fmt_ctx, &enc_pkt);
if (ret < 0)
break;
#endif
}
return ret;
}
void AudioEncoder::start(void)
{
pthread_t encoder;
pthread_create(&encoder, NULL, &AudioEncoder::run, this);
}
AudioEncoder::AudioEncoder() : out_file("test.aac")
{
got_frame = 0;
ret = 0;
size = 0;
av_register_all();
avcodec_register_all();
//Method 1.
pFormatCtx = avformat_alloc_context();
fmt = av_guess_format(NULL, out_file, NULL);
pFormatCtx->oformat = fmt;
#ifdef DUMP_TEST
if (avio_open(&pFormatCtx->pb,out_file, AVIO_FLAG_READ_WRITE) < 0){
cerr << "Failed to open output file!\n";
return;
}
#endif
audio_st = avformat_new_stream(pFormatCtx, 0);
if (audio_st==NULL){
return;
}
pCodecCtx = audio_st->codec;
pCodecCtx->codec_id = fmt->audio_codec;
pCodecCtx->codec_type = AVMEDIA_TYPE_AUDIO;
pCodecCtx->sample_fmt = AV_SAMPLE_FMT_FLTP;
pCodecCtx->sample_rate= 8000;
pCodecCtx->channel_layout=AV_CH_LAYOUT_MONO;
pCodecCtx->channels = av_get_channel_layout_nb_channels(pCodecCtx->channel_layout);
pCodecCtx->bit_rate = 64000;
#ifdef DUMP_TEST
//Show some information
av_dump_format(pFormatCtx, 0, out_file, 1);
#endif
pCodec = avcodec_find_encoder(pCodecCtx->codec_id);
if (!pCodec){
printf("Can not find encoder!\n");
return;
}
if (avcodec_open2(pCodecCtx, pCodec,NULL) < 0){
printf("Failed to open encoder!\n");
return;
}
pFrame = av_frame_alloc();
pFrame->nb_samples= pCodecCtx->frame_size;
pFrame->format= pCodecCtx->sample_fmt;
size = av_samples_get_buffer_size(NULL, pCodecCtx->channels,pCodecCtx->frame_size,pCodecCtx->sample_fmt, 1);
frame_buf = (uint8_t *)av_malloc(size);
avcodec_fill_audio_frame(pFrame, pCodecCtx->channels, pCodecCtx->sample_fmt,(const uint8_t*)frame_buf, size, 1);
//Write Header
#ifdef DUMP_TEST
avformat_write_header(pFormatCtx,NULL);
#endif
}
AudioEncoder::~AudioEncoder()
{
//Flush Encoder
ret = flush_encoder(pFormatCtx,0);
if (ret < 0) {
cerr << "Flushing encoder failed\n";
return;
}
#ifdef DUMP_TEST
//Write Trailer
av_write_trailer(pFormatCtx);
#endif
//Clean
if (audio_st){
avcodec_close(audio_st->codec);
av_free(pFrame);
av_free(frame_buf);
}
avio_close(pFormatCtx->pb);
avformat_free_context(pFormatCtx);
}