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使用ffmpeg实现转码样例(代码实现)
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分類：?C/C++
使用ffmpeg實現轉碼樣例(代碼實現)
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使用ffmpeg轉碼主要工作如下:
Demux -> Decoding -> Encoding -> Muxing
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其中接口調用如下：
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av_register_all();avformat_open_inputavformat_find_stream_infoopen_codec_contextav_image_allocavcodec_alloc_frameavformat_alloc_output_context2avcodec_open2avcodec_alloc_frameavpicture_allocavpicture_allocavformat_write_headerav_init_packetav_read_frameavcodec_decode_video2av_image_copyavcodec_encode_video2av_interleaved_write_frameav_write_trailer ?
下面的代碼為主要將視頻轉碼，封裝為h264編碼格式的mp4文件，音頻為mp3，但是主要操作并不處理音頻文件。代碼如下
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#include?<stdlib.h>
#include?<stdio.h>
#include?<string.h>
#include?<math.h>
#include?<libavutil/opt.h>
#include?<libavutil/mathematics.h>
#include?<libavformat/avformat.h>
#include?<libswscale/swscale.h>
#include?<libswresample/swresample.h>
/*?5 seconds stream duration?*/
#define STREAM_DURATION 200.0#define STREAM_FRAME_RATE 25?/*?25 images/s?*/
#define STREAM_NB_FRAMES?((int)(STREAM_DURATION?*?STREAM_FRAME_RATE))
#define STREAM_PIX_FMT AV_PIX_FMT_YUV420P?/*?default pix_fmt?*/
static AVFormatContext?*input_fmt_ctx?=?NULL;
static?int?sws_flags?=?SWS_BICUBIC;
static AVPacket input_pkt;static?int?video_stream_idx?=?-1;
static uint8_t?*video_dst_data[4]?=?{NULL};
static?int?video_dst_linesize[4];
static AVStream?*input_video_stream;
static AVFrame?*input_frame;
static AVCodecContext?*video_dec_ctx?=?NULL;
static?int?video_dst_bufsize;
static?int?open_codec_context(int?*stream_idx,
?AVFormatContext?*fmt_ctx,?enum AVMediaType type)
{?int?ret;
?AVStream?*st;
?AVCodecContext?*dec_ctx?=?NULL;
?AVCodec?*dec?=?NULL;
?ret?=?av_find_best_stream(fmt_ctx,?type,?-1,?-1,?NULL,?0);
?if?(ret?<?0)?{
?return ret;?}?else?{
?*stream_idx?=?ret;
?st?=?fmt_ctx->streams[*stream_idx];
?/*?find decoder?for?the stream?*/
?dec_ctx?=?st->codec;
?dec?=?avcodec_find_decoder(dec_ctx->codec_id);
?if?(!dec)?{
?fprintf(stderr,?"Failed to find %s codec\n",
?av_get_media_type_string(type));?return ret;?} ?if?((ret?=?avcodec_open2(dec_ctx,?dec,?NULL))?<?0)?{
?fprintf(stderr,?"Failed to open %s codec\n",
?av_get_media_type_string(type));?return ret;?}?} ?return 0;} /*?Add an output stream.?*/
static AVStream?*add_stream(AVFormatContext?*oc,?AVCodec?**codec,
?enum AVCodecID codec_id){?AVCodecContext?*c;
?AVStream?*st;
?/*?find the encoder?*/
?*codec?=?avcodec_find_encoder(codec_id);
?if?(!(*codec))?{
?fprintf(stderr,?"Could not find encoder for '%s'\n",
?avcodec_get_name(codec_id));?exit(1);?} ?st?=?avformat_new_stream(oc,?*codec);
?if?(!st)?{
?fprintf(stderr,?"Could not allocate stream\n");
?exit(1);?}?st->id?=?oc->nb_streams-1;
?c?=?st->codec;
?switch?((*codec)->type)?{
?case?AVMEDIA_TYPE_AUDIO:
?c->sample_fmt?=?AV_SAMPLE_FMT_FLTP;
?c->bit_rate?=?64000;
?c->sample_rate?=?44100;
?c->channels?=?2;
?break; ?case?AVMEDIA_TYPE_VIDEO:
?c->codec_id?=?codec_id;
?c->bit_rate?=?400000;
?c->time_base.den?=?STREAM_FRAME_RATE;
?c->time_base.num?=?1;
?c->gop_size?=?12;?
?c->pix_fmt?=?STREAM_PIX_FMT;
?break; ?default:?break;?} ?/*?Some formats want stream headers?to?be separate.?*/
?if?(oc->oformat->flags?&?AVFMT_GLOBALHEADER)
?c->flags?|=?CODEC_FLAG_GLOBAL_HEADER;
?return st;} /**************************************************************//*?audio output?*/
static float t,?tincr,?tincr2;
static uint8_t?**src_samples_data;
static?int?src_samples_linesize;
static?int?src_nb_samples;
static?int?max_dst_nb_samples;
uint8_t?**dst_samples_data;
int?dst_samples_linesize;
int?dst_samples_size;
struct SwrContext?*swr_ctx?=?NULL;
static void open_audio(AVFormatContext?*oc,?AVCodec?*codec,?AVStream?*st)
{?AVCodecContext?*c;
?int?ret;
?c?=?st->codec;
?/*?open it?*/
?ret?=?avcodec_open2(c,?codec,?NULL);
?if?(ret?<?0)?{
?fprintf(stderr,?"Could not open audio codec: %s\n",?av_err2str(ret));
?exit(1);?} ?/*?init signal generator?*/
?t?=?0;
?tincr?=?2?*?M_PI?*?110.0?/?c->sample_rate;
?/*?increment frequency by 110 Hz per?second?*/
?tincr2?=?2?*?M_PI?*?110.0?/?c->sample_rate?/?c->sample_rate;
?src_nb_samples?=?c->codec->capabilities?&?CODEC_CAP_VARIABLE_FRAME_SIZE??
?10000?:?c->frame_size;
?ret?=?av_samples_alloc_array_and_samples(&src_samples_data,?&src_samples_linesize,?c->channels,
?src_nb_samples,?c->sample_fmt,?0);
?if?(ret?<?0)?{
?fprintf(stderr,?"Could not allocate source samples\n");
?exit(1);?} ?/*?create resampler context?*/
?if?(c->sample_fmt?!=?AV_SAMPLE_FMT_S16)?{
?swr_ctx?=?swr_alloc();
?if?(!swr_ctx)?{
?fprintf(stderr,?"Could not allocate resampler context\n");
?exit(1);?} ?/*?set?options?*/
?av_opt_set_int?(swr_ctx,?"in_channel_count",?c->channels,?0);
?av_opt_set_int?(swr_ctx,?"in_sample_rate",?c->sample_rate,?0);
?av_opt_set_sample_fmt(swr_ctx,?"in_sample_fmt",?AV_SAMPLE_FMT_S16,?0);
?av_opt_set_int?(swr_ctx,?"out_channel_count",?c->channels,?0);
?av_opt_set_int?(swr_ctx,?"out_sample_rate",?c->sample_rate,?0);
?av_opt_set_sample_fmt(swr_ctx,?"out_sample_fmt",?c->sample_fmt,?0);
?/*?initialize the resampling context?*/
?if?((ret?=?swr_init(swr_ctx))?<?0)?{
?fprintf(stderr,?"Failed to initialize the resampling context\n");
?exit(1);?}?} ?/*?compute the number of converted samples:?buffering?is?avoided
??*?ensuring that the output buffer will contain at least all the
??*?converted input samples?*/
?max_dst_nb_samples?=?src_nb_samples;
?ret?=?av_samples_alloc_array_and_samples(&dst_samples_data,?&dst_samples_linesize,?c->channels,
?max_dst_nb_samples,?c->sample_fmt,?0);
?if?(ret?<?0)?{
?fprintf(stderr,?"Could not allocate destination samples\n");
?exit(1);?}?dst_samples_size?=?av_samples_get_buffer_size(NULL,?c->channels,?max_dst_nb_samples,
?c->sample_fmt,?0);
} /*?Prepare a 16 bit dummy audio frame of?'frame_size'?samples?and
?*?'nb_channels'?channels.?*/
static void get_audio_frame(int16_t?*samples,?int?frame_size,?int?nb_channels)
{?int?j,?i,?v;
?int16_t?*q;
?q?=?samples;
?for?(j?=?0;?j?<?frame_size;?j++)?{
?v?=?(int)(sin(t)?*?10000);
?for?(i?=?0;?i?<?nb_channels;?i++)
?*q++?=?v;
?t?+=?tincr;
?tincr?+=?tincr2;
?}} static void write_audio_frame(AVFormatContext?*oc,?AVStream?*st)
{?AVCodecContext?*c;
?AVPacket pkt?=?{?0?};?//?data?and?size must be 0;
?AVFrame?*frame?=?avcodec_alloc_frame();
?int?got_packet,?ret,?dst_nb_samples;
?av_init_packet(&pkt);?c?=?st->codec;
?get_audio_frame((int16_t?*)src_samples_data[0],?src_nb_samples,?c->channels);
?/*?convert samples from native format?to?destination codec format,?using the resampler?*/
?if?(swr_ctx)?{
?/*?compute destination number of samples?*/
?dst_nb_samples?=?av_rescale_rnd(swr_get_delay(swr_ctx,?c->sample_rate)?+?src_nb_samples,
?c->sample_rate,?c->sample_rate,?AV_ROUND_UP);
?if?(dst_nb_samples?>?max_dst_nb_samples)?{
?av_free(dst_samples_data[0]);?ret?=?av_samples_alloc(dst_samples_data,?&dst_samples_linesize,?c->channels,
?dst_nb_samples,?c->sample_fmt,?0);
?if?(ret?<?0)
?exit(1);?max_dst_nb_samples?=?dst_nb_samples;
?dst_samples_size?=?av_samples_get_buffer_size(NULL,?c->channels,?dst_nb_samples,
?c->sample_fmt,?0);
?} ?/*?convert?to?destination format?*/
?ret?=?swr_convert(swr_ctx,
?dst_samples_data,?dst_nb_samples,
?(const?uint8_t?**)src_samples_data,?src_nb_samples);
?if?(ret?<?0)?{
?fprintf(stderr,?"Error while converting\n");
?exit(1);?}?}?else?{
?dst_samples_data[0]?=?src_samples_data[0];
?dst_nb_samples?=?src_nb_samples;
?} ?frame->nb_samples?=?dst_nb_samples;
?avcodec_fill_audio_frame(frame,?c->channels,?c->sample_fmt,
?dst_samples_data[0],?dst_samples_size,?0);
?ret?=?avcodec_encode_audio2(c,?&pkt,?frame,?&got_packet);
?if?(ret?<?0)?{
?fprintf(stderr,?"Error encoding audio frame: %s\n",?av_err2str(ret));
?exit(1);?} ?if?(!got_packet)
?return; ?pkt.stream_index?=?st->index;
?/*?Write the compressed frame?to?the media file.?*/
?ret?=?av_interleaved_write_frame(oc,?&pkt);
?if?(ret?!=?0)?{
?fprintf(stderr,?"Error while writing audio frame: %s\n",
?av_err2str(ret));?exit(1);?}?avcodec_free_frame(&frame);} static void close_audio(AVFormatContext?*oc,?AVStream?*st)
{?avcodec_close(st->codec);?av_free(src_samples_data[0]);?av_free(dst_samples_data[0]);} /***********************bbs.ChinaFFmpeg.com****孫悟空***********************//*?video output?*/
static AVFrame?*frame;
static AVPicture src_picture,?dst_picture;
static?int?frame_count;
static void open_video(AVFormatContext?*oc,?AVCodec?*codec,?AVStream?*st)
{?int?ret;
?AVCodecContext?*c?=?st->codec;
?/*?open the codec?*/
?ret?=?avcodec_open2(c,?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?*/
?frame?=?avcodec_alloc_frame();
?if?(!frame)?{
?fprintf(stderr,?"Could not allocate video frame\n");
?exit(1);?} ?/*?Allocate the encoded raw picture.?*/
?ret?=?avpicture_alloc(&dst_picture,?c->pix_fmt,?c->width,?c->height);
?if?(ret?<?0)?{
?fprintf(stderr,?"Could not allocate picture: %s\n",?av_err2str(ret));
?exit(1);?} ?/*?If?the output format?is?not?YUV420P,?then?a temporary YUV420P
??*?picture?is?needed too.?It?is?then?converted?to?the required
??*?output format.?*/
?if?(c->pix_fmt?!=?AV_PIX_FMT_YUV420P)?{
?ret?=?avpicture_alloc(&src_picture,?AV_PIX_FMT_YUV420P,?c->width,?c->height);
?if?(ret?<?0)?{
?fprintf(stderr,?"Could not allocate temporary picture: %s\n",
?av_err2str(ret));?exit(1);?}?} ?/*?copy data?and?linesize picture pointers?to?frame?*/
?*((AVPicture?*)frame)?=?dst_picture;
} static void write_video_frame(AVFormatContext?*oc,?AVStream?*st)
{?int?ret;
?static struct SwsContext?*sws_ctx;
?AVCodecContext?*c?=?st->codec;
?//?fill_yuv_image(&dst_picture,?frame_count,?c->width,?c->height);
?if?(oc->oformat->flags?&?AVFMT_RAWPICTURE)?{
?/*?Raw video?case?-?directly store the picture?in?the packet?*/
?AVPacket pkt;?av_init_packet(&pkt); ?pkt.flags?|=?AV_PKT_FLAG_KEY;
?pkt.stream_index?=?st->index;
?pkt.data?=?dst_picture.data[0];
?pkt.size?=?sizeof(AVPicture);
?ret?=?av_interleaved_write_frame(oc,?&pkt);
?}?else?{
?AVPacket pkt?=?{?0?};
?int?got_packet;
?av_init_packet(&pkt); ?/*?encode the image?*/
?ret?=?avcodec_encode_video2(c,?&pkt,?frame,?&got_packet);
?if?(ret?<?0)?{
?fprintf(stderr,?"Error encoding video frame: %s\n",?av_err2str(ret));
?exit(1);?}?/*?If?size?is?zero,?it means the image was buffered.?*/
?if?(!ret?&&?got_packet?&&?pkt.size)?{
?pkt.stream_index?=?st->index;
?/*?Write the compressed frame?to?the media file.?*/
?ret?=?av_interleaved_write_frame(oc,?&pkt);
?}?else?{
?ret?=?0;
?}?}?if?(ret?!=?0)?{
?fprintf(stderr,?"Error while writing video frame: %s\n",?av_err2str(ret));
?exit(1);?}?frame_count++;} static void close_video(AVFormatContext?*oc,?AVStream?*st)
{?avcodec_close(st->codec);?av_free(src_picture.data[0]);?av_free(dst_picture.data[0]);?av_free(frame);} /**************************************************************//*?media file output?*/
int?main(int?argc,?char?**argv)
{?const?char?*filename;
?const?char?*input_file;
?AVOutputFormat?*fmt;
?AVFormatContext?*oc;
?AVStream?*audio_st,?*video_st;
?AVCodec?*audio_codec,?*video_codec;
?double audio_time,?video_time;
?int?ret;
?int?decoded;
?int?got_frame;
?/*?Initialize libavcodec,?and?register all codecs?and?formats.?*/
?av_register_all(); ?if?(argc?!=?3)?{
?printf("usage: %s output_file inputfile\n"?"API example program to output a media file with libavformat.\n"?"This program generates a synthetic audio and video stream, encodes and\n"?"muxes them into a file named output_file.\n"?"The output format is automatically guessed according to the file extension.\n"?"Raw images can also be output by using '%%d' in the filename.\n"?"\n",?argv[0]);
?return 1;?} ?input_file?=?argv[2];
?filename?=?argv[1];
?if?(avformat_open_input(?&input_fmt_ctx,?input_file,?NULL,?NULL)?<?0)?{
?fprintf(stderr,?"Could not open source file %s\n",?input_file);
?exit(-1);?} ?/*?retrieve stream information?*/
?if?(avformat_find_stream_info(input_fmt_ctx,?NULL)?<?0)?{
?fprintf(stderr,?"Could not find stream information\n");
?exit(1);?} ?if?(open_codec_context(&video_stream_idx,?input_fmt_ctx,?AVMEDIA_TYPE_VIDEO)?>=?0)?{
?input_video_stream?=?input_fmt_ctx->streams[video_stream_idx];
?video_dec_ctx?=?input_video_stream->codec;
?ret?=?av_image_alloc(video_dst_data,?video_dst_linesize,
?video_dec_ctx->width,?video_dec_ctx->height,
?video_dec_ctx->pix_fmt,?1);
?if?(ret?<?0)?{
?fprintf(stderr,?"Could not allocate raw video buffer\n");
?}?video_dst_bufsize?=?ret;
?} ?input_frame?=?avcodec_alloc_frame();
?if?(!input_frame)?{
?fprintf(stderr,?"Could not allocate frame\n");
?ret?=?AVERROR(ENOMEM);
?exit(-1);?} ?/*?allocate the output media context?*/
?avformat_alloc_output_context2(&oc,?NULL,?NULL,?filename);
?if?(!oc)?{
?printf("Could not deduce output format from file extension: using MPEG.\n");?avformat_alloc_output_context2(&oc,?NULL,?"mpeg",?filename);
?}?if?(!oc)?{
?return 1;?}?fmt?=?oc->oformat;
?video_st?=?NULL;
?audio_st?=?NULL;
?fmt->video_codec?=?AV_CODEC_ID_H264;
?if?(fmt->video_codec?!=?AV_CODEC_ID_NONE)?{
?video_st?=?add_stream(oc,?&video_codec,?AV_CODEC_ID_H264);
?}?if?(video_st->codec)?{
?video_st->codec->width?=?video_dec_ctx->width;
?video_st->codec->height?=?video_dec_ctx->height;
?}?fmt->audio_codec?=?AV_CODEC_ID_MP3;
?if?(fmt->audio_codec?!=?AV_CODEC_ID_NONE)?{
?audio_st?=?add_stream(oc,?&audio_codec,?AV_CODEC_ID_MP3);
?} ?/*?Now?that all the parameters are?set,?we can open the audio?and
??*?video codecs?and?allocate the necessary encode buffers.?*/
?if?(video_st)
?open_video(oc,?video_codec,?video_st);
?if?(audio_st)
?open_audio(oc,?audio_codec,?audio_st);
?av_dump_format(oc,?0,?filename,?1);
?/*?open the output file,?if?needed?*/
?if?(!(fmt->flags?&?AVFMT_NOFILE))?{
?ret?=?avio_open(&oc->pb,?filename,?AVIO_FLAG_WRITE);
?if?(ret?<?0)?{
?fprintf(stderr,?"Could not open '%s': %s\n",?filename,
?av_err2str(ret));?return 1;?}?} ?/*?Write the stream header,?if?any.?*/
?ret?=?avformat_write_header(oc,?NULL);
?if?(ret?<?0)?{
?fprintf(stderr,?"Error occurred when opening output file: %s\n",
?av_err2str(ret));?return 1;?} ?av_init_packet(&input_pkt);?input_pkt.data?=?NULL;
?input_pkt.size?=?0;
?if?(frame)
?frame->pts?=?0;
?for?(;;)?{
?/*?Compute current audio?and?video?time.?*/
?audio_time?=?audio_st???audio_st->pts.val?*?av_q2d(audio_st->time_base)?:?0.0;
?video_time?=?video_st???video_st->pts.val?*?av_q2d(video_st->time_base)?:?0.0;
?if?((!audio_st?||?audio_time?>=?STREAM_DURATION)?&&
?(!video_st?||?video_time?>=?STREAM_DURATION))
?break; ?/*?write interleaved audio?and?video frames?*/
?if?(!video_st?||?(video_st?&&?audio_st?&&?audio_time?<?video_time))?{
?write_audio_frame(oc,?audio_st);
?}?else?{
?av_read_frame(input_fmt_ctx,?&input_pkt);
?decoded?=?input_pkt.size;
?if?(input_pkt.stream_index?==?video_stream_idx)?{
?/*?decode video frame?*/
?ret?=?avcodec_decode_video2(video_dec_ctx,?input_frame,?&got_frame,?&input_pkt);
?if?(ret?<?0)?{
?fprintf(stderr,?"Error decoding video frame\n");
?return ret;?} ?if?(got_frame)?{
?av_image_copy(&dst_picture,?video_dst_linesize,
?(const?uint8_t?**)(input_frame->data),?input_frame->linesize,
?video_dec_ctx->pix_fmt,?video_dec_ctx->width,?video_dec_ctx->height);
?}?}?
?write_video_frame(oc,?video_st);
?frame->pts?+=?av_rescale_q(1,?video_st->codec->time_base,?video_st->time_base);
?}?} ?av_write_trailer(oc); ?/*?Close?each?codec.?*/
?if?(video_st)
?close_video(oc,?video_st);
?if?(audio_st)
?close_audio(oc,?audio_st);
?if?(!(fmt->flags?&?AVFMT_NOFILE))
?avio_close(oc->pb); ?avformat_free_context(oc);?av_free(input_frame);?av_free(video_dst_data[0]);?avcodec_close(video_dec_ctx);?return 0;} 以上代碼為從dox/example/muxing.c中修改得到
編譯命令如下：
點擊(此處)折疊或打開
gcc?-g doc/examples/muxing.c?-o muxing?-lavcodec?-lavdevice?-lavfilter?-lavformat?-lavutil?-lswscale?-lswresample?-lpostproc?-lx264?-lmp3lame?-lz?-liconv?-lbz2 執行命令如下：
點擊(此處)折疊或打開
執行后效果如下：
查看轉碼完成后的多媒體文件的信息：
查看轉碼后的文件的視頻:
轉載于:https://www.cnblogs.com/android-blogs/p/5663149.html
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