ffmpeg音频转码，采用swr_convert重取样

1、概述：

和上一篇音频转码流程一样，只是把filter重取样改为了swr_convert重取样，理解本例子对AVFrame中data如何存储音频数据有更好的理解。

2、代码：

/**最简单的音频转码器（只处理音频）*缪国凯 Mickel*[e-mail]*本程序实现从一个视频格式转码到另一个视频格式，只处理音频，视频忽略，若有多个音频流，只处理第一个,采用swr_convert重取样*2015-5-8*/#include "stdafx.h"#ifdef __cplusplusextern"C"{#endif#include <libavformat/avformat.h>#include "libavcodec/avcodec.h"#include "libavfilter/avfiltergraph.h"#include "libavfilter/buffersink.h"#include "libavfilter/buffersrc.h"#include "libavutil/avutil.h"#include "libavutil/opt.h"#include "libavutil/pixdesc.h"#include "libswresample\swresample.h"#include "libavutil\fifo.h"#pragma comment(lib, "avcodec.lib")#pragma comment(lib, "avformat.lib")#pragma comment(lib, "avutil.lib")//#pragma comment(lib, "avdevice.lib")#pragma comment(lib, "avfilter.lib")//#pragma comment(lib, "postproc.lib")#pragma comment(lib, "swresample.lib")//#pragma comment(lib, "swscale.lib")#ifdef __cplusplus};#endif#define BUF_SIZE_20K 2048000#define BUF_SIZE_1K 1024000SwrContext* pSwrCtx = NULL;AVStream *out_stream = NULL;AVFormatContext *in_fmt_ctx = NULL, *out_fmt_ctx = NULL;int audio_index = -1;void initSwr(){if (out_fmt_ctx->streams[0]->codec->channels != in_fmt_ctx->streams[audio_index]->codec->channels|| out_fmt_ctx->streams[0]->codec->sample_rate != in_fmt_ctx->streams[audio_index]->codec->sample_rate|| out_fmt_ctx->streams[0]->codec->sample_fmt != in_fmt_ctx->streams[audio_index]->codec->sample_fmt){if ( NULL == pSwrCtx ) {pSwrCtx = swr_alloc();}#if LIBSWRESAMPLE_VERSION_MINOR >= 17// 根据版本不同，选用适当函数av_opt_set_int(pSwrCtx, "ich", in_fmt_ctx->streams[audio_index]->codec->channels, 0);av_opt_set_int(pSwrCtx, "och", out_fmt_ctx->streams[0]->codec->channels, 0);av_opt_set_int(pSwrCtx, "in_sample_rate",  in_fmt_ctx->streams[audio_index]->codec->sample_rate, 0);av_opt_set_int(pSwrCtx, "out_sample_rate",  out_fmt_ctx->streams[0]->codec->sample_rate, 0);av_opt_set_sample_fmt(pSwrCtx, "in_sample_fmt", in_fmt_ctx->streams[audio_index]->codec->sample_fmt, 0);av_opt_set_sample_fmt(pSwrCtx, "out_sample_fmt", out_fmt_ctx->streams[0]->codec->sample_fmt, 0);#elsepSwrCtx = swr_alloc_set_opts(pSwrCtx,out_fmt_ctx->streams[0]->codec->channel_layout, out_fmt_ctx->streams[0]->codec->sample_fmt, out_fmt_ctx->streams[0]->codec->->sample_rate,in_fmt_ctx->streams[audio_index]->codec->channel_layout, in_fmt_ctx->streams[audio_index]->codec->sample_fmt, in_fmt_ctx->streams[audio_index]->codec->sample_rate,0, NULL);#endifswr_init(pSwrCtx);}}//setup_array函数摘自ffmpeg例程static void setup_array(uint8_t* out[SWR_CH_MAX], AVFrame* in_frame, int format, int samples){if (av_sample_fmt_is_planar((AVSampleFormat)format)) {int i;int plane_size = av_get_bytes_per_sample((AVSampleFormat)(format & 0xFF)) * samples;format &= 0xFF;//从decoder出来的frame中的data数据不是连续分布的，所以不能这样写：in_frame->data[0]+i*plane_size;for (i = 0; i < in_frame->channels; i++){out[i] = in_frame->data[i];}} else{out[0] = in_frame->data[0];}}int TransSample(AVFrame *in_frame, AVFrame *out_frame){int ret;int max_dst_nb_samples = 4096;//int64_t dst_nb_samples;int64_t src_nb_samples = in_frame->nb_samples;out_frame->pts = in_frame->pts;uint8_t* paudiobuf;int decode_size, input_size, len;if (pSwrCtx != NULL) {out_frame->nb_samples = av_rescale_rnd(swr_get_delay(pSwrCtx, out_fmt_ctx->streams[0]->codec->sample_rate) + src_nb_samples,out_fmt_ctx->streams[0]->codec->sample_rate, in_fmt_ctx->streams[audio_index]->codec->sample_rate, AV_ROUND_UP);ret = av_samples_alloc(out_frame->data, &out_frame->linesize[0], out_fmt_ctx->streams[0]->codec->channels, out_frame->nb_samples, out_fmt_ctx->streams[0]->codec->sample_fmt, 0);if (ret < 0){av_log(NULL, AV_LOG_WARNING, "[%s.%d %s() Could not allocate samples Buffer\n", __FILE__, __LINE__, __FUNCTION__);return -1;}max_dst_nb_samples = out_frame->nb_samples;//输入也可能是分平面的，所以要做如下处理uint8_t* m_ain[SWR_CH_MAX];setup_array(m_ain, in_frame, in_fmt_ctx->streams[audio_index]->codec->sample_fmt, src_nb_samples);//注意这里，out_count和in_count是samples单位，不是byte//所以这样av_get_bytes_per_sample(in_fmt_ctx->streams[audio_index]->codec->sample_fmt) * src_nb_samples是错的len = swr_convert(pSwrCtx, out_frame->data, out_frame->nb_samples, (const uint8_t**)m_ain, src_nb_samples);if (len < 0){char errmsg[BUF_SIZE_1K];av_strerror(len, errmsg, sizeof(errmsg));av_log(NULL, AV_LOG_WARNING, "[%s:%d] swr_convert!(%d)(%s)", __FILE__, __LINE__, len, errmsg);return -1;}}else{printf("pSwrCtx with out init!\n");return -1;}return 0;}int 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;}int i = 0;while(1){enc_pkt.data = NULL;enc_pkt.size = 0;av_init_packet(&enc_pkt);ret = avcodec_encode_audio2(out_fmt_ctx->streams[stream_index]->codec, &enc_pkt,NULL, &got_frame);if (ret < 0)break;if (!got_frame)break;/* prepare packet for muxing */enc_pkt.stream_index = stream_index;enc_pkt.dts = av_rescale_q_rnd(enc_pkt.dts,out_fmt_ctx->streams[stream_index]->codec->time_base,out_fmt_ctx->streams[stream_index]->time_base,(AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));enc_pkt.pts = av_rescale_q_rnd(enc_pkt.pts,out_fmt_ctx->streams[stream_index]->codec->time_base,out_fmt_ctx->streams[stream_index]->time_base,(AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));enc_pkt.duration = av_rescale_q(enc_pkt.duration,out_fmt_ctx->streams[stream_index]->codec->time_base,out_fmt_ctx->streams[stream_index]->time_base);/* mux encoded frame */ret = av_interleaved_write_frame(out_fmt_ctx, &enc_pkt);av_free_packet(&enc_pkt);if (ret < 0){break;}i++;}printf("flusher write %d frame", i);return ret;}int _tmain(int argc, _TCHAR* argv[]){AVFrame *frame, *frame_out;AVPacket pkt_in, pkt_out;int ret;if (argc < 3){printf("error in input param");getchar();return -1;}av_register_all();avfilter_register_all();//inputif (avformat_open_input(&in_fmt_ctx, argv[1], NULL, NULL) < 0){printf("can not open input file context");goto end;}if (avformat_find_stream_info(in_fmt_ctx, NULL) < 0){printf("can not find input stream info!\n");goto end;}//outputavformat_alloc_output_context2(&out_fmt_ctx, NULL, NULL, argv[2]);if (!out_fmt_ctx){printf("can not alloc output context!\n");goto end;}//open decoder & new out stream & open encoderfor (int i = 0; i < in_fmt_ctx->nb_streams; i++){if (in_fmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO){//open decoderif(0 > avcodec_open2(in_fmt_ctx->streams[i]->codec, avcodec_find_decoder(in_fmt_ctx->streams[i]->codec->codec_id), NULL)){printf("can not find or open decoder!\n");goto end;}audio_index = i;//new streamout_stream = avformat_new_stream(out_fmt_ctx, NULL);if (!out_stream){printf("can not new stream for output!\n");goto end;}//set codec context param//use default audio encoderout_stream->codec->codec = avcodec_find_encoder(out_fmt_ctx->oformat->audio_codec);//use the input audio encoder//out_stream->codec->codec = avcodec_find_encoder(in_fmt_ctx->streams[i]->codec->codec_id);out_stream->codec->sample_rate = in_fmt_ctx->streams[i]->codec->sample_rate;out_stream->codec->channel_layout = in_fmt_ctx->streams[i]->codec->channel_layout;out_stream->codec->channels = av_get_channel_layout_nb_channels(out_stream->codec->channel_layout);// take first format from list of supported formatsout_stream->codec->sample_fmt = out_stream->codec->codec->sample_fmts[0];AVRational time_base={1, out_stream->codec->sample_rate};out_stream->codec->time_base = time_base;//open encoderif (!out_stream->codec->codec){printf("can not find the encoder!\n");goto end;}if ((avcodec_open2(out_stream->codec, out_stream->codec->codec, NULL)) < 0){printf("can not open the encoder\n");goto end;}if (out_fmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;break;}}//dump input infoav_dump_format(in_fmt_ctx, 0, argv[1], 0);//dump output infoav_dump_format(out_fmt_ctx, 0, argv[2], 1);if (-1 == audio_index){printf("found no audio stream in input file!\n");goto end;}if (!(out_fmt_ctx->oformat->flags & AVFMT_NOFILE)){if(avio_open(&out_fmt_ctx->pb, argv[2], AVIO_FLAG_WRITE) < 0){printf("can not open output file handle!\n");goto end;}}if(avformat_write_header(out_fmt_ctx, NULL) < 0){printf("can not write the header of the output file!\n");goto end;}//initSwr();int got_frame, got_picture;int frame_index = 0;int i = 0;for(int i = 0; ;i++){pkt_in.data = NULL;pkt_in.size = 0;got_frame = -1;got_picture = -1;if (av_read_frame(in_fmt_ctx, &pkt_in) < 0){break;}if (pkt_in.stream_index != audio_index){continue;}frame = av_frame_alloc();if ((ret = avcodec_decode_audio4(in_fmt_ctx->streams[audio_index]->codec, frame, &got_frame, &pkt_in)) < 0){av_frame_free(&frame);printf("can not decoder a frame");break;}av_free_packet(&pkt_in);if (got_frame){frame->pts = av_frame_get_best_effort_timestamp(frame);frame_out = av_frame_alloc();if (0 != TransSample(frame, frame_out)){printf("can not swr the audio data!\n");break;}av_init_packet(&pkt_out);int ret = avcodec_encode_audio2(out_fmt_ctx->streams[0]->codec, &pkt_out, frame_out, &got_picture);av_free(frame_out->data[0]);av_frame_free(&frame_out);if (got_picture ) {pkt_out.stream_index = out_stream->index;pkt_out.dts = av_rescale_q_rnd(pkt_out.dts,out_fmt_ctx->streams[out_stream->index]->codec->time_base,out_fmt_ctx->streams[out_stream->index]->time_base,(AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));pkt_out.pts = av_rescale_q_rnd(pkt_out.pts,out_fmt_ctx->streams[out_stream->index]->codec->time_base,out_fmt_ctx->streams[out_stream->index]->time_base,(AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));pkt_out.duration = av_rescale_q(pkt_out.duration,out_fmt_ctx->streams[out_stream->index]->codec->time_base,out_fmt_ctx->streams[out_stream->index]->time_base);av_log(NULL, AV_LOG_DEBUG, "Muxing frame\n");/* mux encoded frame */ret = av_interleaved_write_frame(out_fmt_ctx, &pkt_out);av_free_packet(&pkt_out);if (ret < 0){printf("write a frame failed!\n");break;}printf("success write a frame:index %d\n", frame_index++);}}}ret = flush_encoder(out_fmt_ctx, out_stream->index);if (ret < 0){printf("Flushing encoder failed");return -1;}//write file trailerav_write_trailer(out_fmt_ctx);//cleanavcodec_close(out_stream->codec);avcodec_close(in_fmt_ctx->streams[audio_index]->codec);end:avformat_close_input(&in_fmt_ctx);if (out_fmt_ctx && !(out_fmt_ctx->oformat->flags & AVFMT_NOFILE)){avio_close(out_fmt_ctx->pb);}avformat_free_context(out_fmt_ctx);getchar();return 0;}

3、工程下载地址：

http://download.csdn.net/detail/dancing_night/8685669