首页
学习
活动
专区
工具
TVP
发布
社区首页 >专栏 >使用ffmpeg实现转码样例(代码实现)

使用ffmpeg实现转码样例(代码实现)

作者头像
用户3765803
发布2019-03-05 09:41:23
1.1K0
发布2019-03-05 09:41:23
举报
文章被收录于专栏:悟空被FFmpeg玩悟空被FFmpeg玩

使用ffmpeg实现转码样例(代码实现)

使用ffmpeg转码主要工作如下:

Demux -> Decoding -> Encoding -> Muxing

其中接口调用如下:

点击(此处)折叠或打开

  1. av_register_all();
  2. avformat_open_input
  3. avformat_find_stream_info
  4. open_codec_context
  5. av_image_alloc
  6. avcodec_alloc_frame
  7. avformat_alloc_output_context2
  8. avcodec_open2
  9. avcodec_alloc_frame
  10. avpicture_alloc
  11. avpicture_alloc
  12. avformat_write_header
  13. av_init_packet
  14. av_read_frame
  15. avcodec_decode_video2
  16. av_image_copy
  17. avcodec_encode_video2
  18. av_interleaved_write_frame
  19. av_write_trailer

下面的代码为主要将视频转码,封装为h264编码格式的mp4文件,音频为mp3,但是主要操作并不处理音频文件。代码如下

点击(此处)折叠或打开

  1. #include <stdlib.h>
  2. #include <stdio.h>
  3. #include <string.h>
  4. #include <math.h>
  5. #include <libavutil/opt.h>
  6. #include <libavutil/mathematics.h>
  7. #include <libavformat/avformat.h>
  8. #include <libswscale/swscale.h>
  9. #include <libswresample/swresample.h>
  10. /* 5 seconds stream duration */
  11. #define STREAM_DURATION 200.0
  12. #define STREAM_FRAME_RATE 25 /* 25 images/s */
  13. #define STREAM_NB_FRAMES ((int)(STREAM_DURATION * STREAM_FRAME_RATE))
  14. #define STREAM_PIX_FMT AV_PIX_FMT_YUV420P /* default pix_fmt */
  15. static AVFormatContext *input_fmt_ctx = NULL;
  16. static int sws_flags = SWS_BICUBIC;
  17. static AVPacket input_pkt;
  18. static int video_stream_idx = -1;
  19. static uint8_t *video_dst_data[4] = {NULL};
  20. static int video_dst_linesize[4];
  21. static AVStream *input_video_stream;
  22. static AVFrame *input_frame;
  23. static AVCodecContext *video_dec_ctx = NULL;
  24. static int video_dst_bufsize;
  25. static int open_codec_context(int *stream_idx,
  26.  AVFormatContext *fmt_ctx, enum AVMediaType type)
  27. {
  28. int ret;
  29.  AVStream *st;
  30.  AVCodecContext *dec_ctx = NULL;
  31.  AVCodec *dec = NULL;
  32.  ret = av_find_best_stream(fmt_ctx, type, -1, -1, NULL, 0);
  33. if (ret < 0) {
  34.  return ret;
  35. } else {
  36. *stream_idx = ret;
  37.  st = fmt_ctx->streams[*stream_idx];
  38. /* find decoder for the stream */
  39.  dec_ctx = st->codec;
  40.  dec = avcodec_find_decoder(dec_ctx->codec_id);
  41. if (!dec) {
  42.  fprintf(stderr, "Failed to find %s codec\n",
  43.  av_get_media_type_string(type));
  44.  return ret;
  45. }
  46. if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
  47.  fprintf(stderr, "Failed to open %s codec\n",
  48.  av_get_media_type_string(type));
  49.  return ret;
  50. }
  51. }
  52.  return 0;
  53. }
  54. /* Add an output stream. */
  55. static AVStream *add_stream(AVFormatContext *oc, AVCodec **codec,
  56.  enum AVCodecID codec_id)
  57. {
  58.  AVCodecContext *c;
  59.  AVStream *st;
  60. /* find the encoder */
  61. *codec = avcodec_find_encoder(codec_id);
  62. if (!(*codec)) {
  63.  fprintf(stderr, "Could not find encoder for '%s'\n",
  64.  avcodec_get_name(codec_id));
  65. exit(1);
  66. }
  67.  st = avformat_new_stream(oc, *codec);
  68. if (!st) {
  69.  fprintf(stderr, "Could not allocate stream\n");
  70. exit(1);
  71. }
  72.  st->id = oc->nb_streams-1;
  73.  c = st->codec;
  74.  switch ((*codec)->type) {
  75. case AVMEDIA_TYPE_AUDIO:
  76.  c->sample_fmt = AV_SAMPLE_FMT_FLTP;
  77.  c->bit_rate = 64000;
  78.  c->sample_rate = 44100;
  79.  c->channels = 2;
  80.  break;
  81. case AVMEDIA_TYPE_VIDEO:
  82.  c->codec_id = codec_id;
  83.  c->bit_rate = 400000;
  84.  c->time_base.den = STREAM_FRAME_RATE;
  85.  c->time_base.num = 1;
  86.  c->gop_size = 12;
  87.  c->pix_fmt = STREAM_PIX_FMT;
  88.  break;
  89.  default:
  90.  break;
  91. }
  92. /* Some formats want stream headers to be separate. */
  93. if (oc->oformat->flags & AVFMT_GLOBALHEADER)
  94.  c->flags |= CODEC_FLAG_GLOBAL_HEADER;
  95.  return st;
  96. }
  97. /**************************************************************/
  98. /* audio output */
  99. static float t, tincr, tincr2;
  100. static uint8_t **src_samples_data;
  101. static int src_samples_linesize;
  102. static int src_nb_samples;
  103. static int max_dst_nb_samples;
  104. uint8_t **dst_samples_data;
  105. int dst_samples_linesize;
  106. int dst_samples_size;
  107. struct SwrContext *swr_ctx = NULL;
  108. static void open_audio(AVFormatContext *oc, AVCodec *codec, AVStream *st)
  109. {
  110.  AVCodecContext *c;
  111. int ret;
  112.  c = st->codec;
  113. /* open it */
  114.  ret = avcodec_open2(c, codec, NULL);
  115. if (ret < 0) {
  116.  fprintf(stderr, "Could not open audio codec: %s\n", av_err2str(ret));
  117. exit(1);
  118. }
  119. /* init signal generator */
  120.  t = 0;
  121.  tincr = 2 * M_PI * 110.0 / c->sample_rate;
  122. /* increment frequency by 110 Hz per second */
  123.  tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
  124.  src_nb_samples = c->codec->capabilities & CODEC_CAP_VARIABLE_FRAME_SIZE ?
  125.  10000 : c->frame_size;
  126.  ret = av_samples_alloc_array_and_samples(&src_samples_data, &src_samples_linesize, c->channels,
  127.  src_nb_samples, c->sample_fmt, 0);
  128. if (ret < 0) {
  129.  fprintf(stderr, "Could not allocate source samples\n");
  130. exit(1);
  131. }
  132. /* create resampler context */
  133. if (c->sample_fmt != AV_SAMPLE_FMT_S16) {
  134.  swr_ctx = swr_alloc();
  135. if (!swr_ctx) {
  136.  fprintf(stderr, "Could not allocate resampler context\n");
  137. exit(1);
  138. }
  139. /* set options */
  140.  av_opt_set_int (swr_ctx, "in_channel_count", c->channels, 0);
  141.  av_opt_set_int (swr_ctx, "in_sample_rate", c->sample_rate, 0);
  142.  av_opt_set_sample_fmt(swr_ctx, "in_sample_fmt", AV_SAMPLE_FMT_S16, 0);
  143.  av_opt_set_int (swr_ctx, "out_channel_count", c->channels, 0);
  144.  av_opt_set_int (swr_ctx, "out_sample_rate", c->sample_rate, 0);
  145.  av_opt_set_sample_fmt(swr_ctx, "out_sample_fmt", c->sample_fmt, 0);
  146. /* initialize the resampling context */
  147. if ((ret = swr_init(swr_ctx)) < 0) {
  148.  fprintf(stderr, "Failed to initialize the resampling context\n");
  149. exit(1);
  150. }
  151. }
  152. /* compute the number of converted samples: buffering is avoided
  153. * ensuring that the output buffer will contain at least all the
  154. * converted input samples */
  155.  max_dst_nb_samples = src_nb_samples;
  156.  ret = av_samples_alloc_array_and_samples(&dst_samples_data, &dst_samples_linesize, c->channels,
  157.  max_dst_nb_samples, c->sample_fmt, 0);
  158. if (ret < 0) {
  159.  fprintf(stderr, "Could not allocate destination samples\n");
  160. exit(1);
  161. }
  162.  dst_samples_size = av_samples_get_buffer_size(NULL, c->channels, max_dst_nb_samples,
  163.  c->sample_fmt, 0);
  164. }
  165. /* Prepare a 16 bit dummy audio frame of 'frame_size' samples and
  166. * 'nb_channels' channels. */
  167. static void get_audio_frame(int16_t *samples, int frame_size, int nb_channels)
  168. {
  169. int j, i, v;
  170.  int16_t *q;
  171.  q = samples;
  172. for (j = 0; j < frame_size; j++) {
  173.  v = (int)(sin(t) * 10000);
  174. for (i = 0; i < nb_channels; i++)
  175. *q++ = v;
  176.  t += tincr;
  177.  tincr += tincr2;
  178. }
  179. }
  180. static void write_audio_frame(AVFormatContext *oc, AVStream *st)
  181. {
  182.  AVCodecContext *c;
  183.  AVPacket pkt = { 0 }; // data and size must be 0;
  184.  AVFrame *frame = avcodec_alloc_frame();
  185. int got_packet, ret, dst_nb_samples;
  186.  av_init_packet(&pkt);
  187.  c = st->codec;
  188.  get_audio_frame((int16_t *)src_samples_data[0], src_nb_samples, c->channels);
  189. /* convert samples from native format to destination codec format, using the resampler */
  190. if (swr_ctx) {
  191. /* compute destination number of samples */
  192.  dst_nb_samples = av_rescale_rnd(swr_get_delay(swr_ctx, c->sample_rate) + src_nb_samples,
  193.  c->sample_rate, c->sample_rate, AV_ROUND_UP);
  194. if (dst_nb_samples > max_dst_nb_samples) {
  195.  av_free(dst_samples_data[0]);
  196.  ret = av_samples_alloc(dst_samples_data, &dst_samples_linesize, c->channels,
  197.  dst_nb_samples, c->sample_fmt, 0);
  198. if (ret < 0)
  199. exit(1);
  200.  max_dst_nb_samples = dst_nb_samples;
  201.  dst_samples_size = av_samples_get_buffer_size(NULL, c->channels, dst_nb_samples,
  202.  c->sample_fmt, 0);
  203. }
  204. /* convert to destination format */
  205.  ret = swr_convert(swr_ctx,
  206.  dst_samples_data, dst_nb_samples,
  207. (const uint8_t **)src_samples_data, src_nb_samples);
  208. if (ret < 0) {
  209.  fprintf(stderr, "Error while converting\n");
  210. exit(1);
  211. }
  212. } else {
  213.  dst_samples_data[0] = src_samples_data[0];
  214.  dst_nb_samples = src_nb_samples;
  215. }
  216.  frame->nb_samples = dst_nb_samples;
  217.  avcodec_fill_audio_frame(frame, c->channels, c->sample_fmt,
  218.  dst_samples_data[0], dst_samples_size, 0);
  219.  ret = avcodec_encode_audio2(c, &pkt, frame, &got_packet);
  220. if (ret < 0) {
  221.  fprintf(stderr, "Error encoding audio frame: %s\n", av_err2str(ret));
  222. exit(1);
  223. }
  224. if (!got_packet)
  225.  return;
  226.  pkt.stream_index = st->index;
  227. /* Write the compressed frame to the media file. */
  228.  ret = av_interleaved_write_frame(oc, &pkt);
  229. if (ret != 0) {
  230.  fprintf(stderr, "Error while writing audio frame: %s\n",
  231.  av_err2str(ret));
  232. exit(1);
  233. }
  234.  avcodec_free_frame(&frame);
  235. }
  236. static void close_audio(AVFormatContext *oc, AVStream *st)
  237. {
  238.  avcodec_close(st->codec);
  239.  av_free(src_samples_data[0]);
  240.  av_free(dst_samples_data[0]);
  241. }
  242. /***********************bbs.ChinaFFmpeg.com****孙悟空***********************/
  243. /* video output */
  244. static AVFrame *frame;
  245. static AVPicture src_picture, dst_picture;
  246. static int frame_count;
  247. static void open_video(AVFormatContext *oc, AVCodec *codec, AVStream *st)
  248. {
  249. int ret;
  250.  AVCodecContext *c = st->codec;
  251. /* open the codec */
  252.  ret = avcodec_open2(c, codec, NULL);
  253. if (ret < 0) {
  254.  fprintf(stderr, "Could not open video codec: %s\n", av_err2str(ret));
  255. exit(1);
  256. }
  257. /* allocate and init a re-usable frame */
  258.  frame = avcodec_alloc_frame();
  259. if (!frame) {
  260.  fprintf(stderr, "Could not allocate video frame\n");
  261. exit(1);
  262. }
  263. /* Allocate the encoded raw picture. */
  264.  ret = avpicture_alloc(&dst_picture, c->pix_fmt, c->width, c->height);
  265. if (ret < 0) {
  266.  fprintf(stderr, "Could not allocate picture: %s\n", av_err2str(ret));
  267. exit(1);
  268. }
  269. /* If the output format is not YUV420P, then a temporary YUV420P
  270. * picture is needed too. It is then converted to the required
  271. * output format. */
  272. if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
  273.  ret = avpicture_alloc(&src_picture, AV_PIX_FMT_YUV420P, c->width, c->height);
  274. if (ret < 0) {
  275.  fprintf(stderr, "Could not allocate temporary picture: %s\n",
  276.  av_err2str(ret));
  277. exit(1);
  278. }
  279. }
  280. /* copy data and linesize picture pointers to frame */
  281. *((AVPicture *)frame) = dst_picture;
  282. }
  283. static void write_video_frame(AVFormatContext *oc, AVStream *st)
  284. {
  285. int ret;
  286.  static struct SwsContext *sws_ctx;
  287.  AVCodecContext *c = st->codec;
  288. // fill_yuv_image(&dst_picture, frame_count, c->width, c->height);
  289. if (oc->oformat->flags & AVFMT_RAWPICTURE) {
  290. /* Raw video case - directly store the picture in the packet */
  291.  AVPacket pkt;
  292.  av_init_packet(&pkt);
  293.  pkt.flags |= AV_PKT_FLAG_KEY;
  294.  pkt.stream_index = st->index;
  295.  pkt.data = dst_picture.data[0];
  296.  pkt.size = sizeof(AVPicture);
  297.  ret = av_interleaved_write_frame(oc, &pkt);
  298. } else {
  299.  AVPacket pkt = { 0 };
  300. int got_packet;
  301.  av_init_packet(&pkt);
  302. /* encode the image */
  303.  ret = avcodec_encode_video2(c, &pkt, frame, &got_packet);
  304. if (ret < 0) {
  305.  fprintf(stderr, "Error encoding video frame: %s\n", av_err2str(ret));
  306. exit(1);
  307. }
  308. /* If size is zero, it means the image was buffered. */
  309. if (!ret && got_packet && pkt.size) {
  310.  pkt.stream_index = st->index;
  311. /* Write the compressed frame to the media file. */
  312.  ret = av_interleaved_write_frame(oc, &pkt);
  313. } else {
  314.  ret = 0;
  315. }
  316. }
  317. if (ret != 0) {
  318.  fprintf(stderr, "Error while writing video frame: %s\n", av_err2str(ret));
  319. exit(1);
  320. }
  321.  frame_count++;
  322. }
  323. static void close_video(AVFormatContext *oc, AVStream *st)
  324. {
  325.  avcodec_close(st->codec);
  326.  av_free(src_picture.data[0]);
  327.  av_free(dst_picture.data[0]);
  328.  av_free(frame);
  329. }
  330. /**************************************************************/
  331. /* media file output */
  332. int main(int argc, char **argv)
  333. {
  334. const char *filename;
  335. const char *input_file;
  336.  AVOutputFormat *fmt;
  337.  AVFormatContext *oc;
  338.  AVStream *audio_st, *video_st;
  339.  AVCodec *audio_codec, *video_codec;
  340.  double audio_time, video_time;
  341. int ret;
  342. int decoded;
  343. int got_frame;
  344. /* Initialize libavcodec, and register all codecs and formats. */
  345.  av_register_all();
  346. if (argc != 3) {
  347.  printf("usage: %s output_file inputfile\n"
  348. "API example program to output a media file with libavformat.\n"
  349. "This program generates a synthetic audio and video stream, encodes and\n"
  350. "muxes them into a file named output_file.\n"
  351. "The output format is automatically guessed according to the file extension.\n"
  352. "Raw images can also be output by using '%%d' in the filename.\n"
  353. "\n", argv[0]);
  354.  return 1;
  355. }
  356.  input_file = argv[2];
  357.  filename = argv[1];
  358. if (avformat_open_input( &input_fmt_ctx, input_file, NULL, NULL) < 0) {
  359.  fprintf(stderr, "Could not open source file %s\n", input_file);
  360. exit(-1);
  361. }
  362. /* retrieve stream information */
  363. if (avformat_find_stream_info(input_fmt_ctx, NULL) < 0) {
  364.  fprintf(stderr, "Could not find stream information\n");
  365. exit(1);
  366. }
  367. if (open_codec_context(&video_stream_idx, input_fmt_ctx, AVMEDIA_TYPE_VIDEO) >= 0) {
  368.  input_video_stream = input_fmt_ctx->streams[video_stream_idx];
  369.  video_dec_ctx = input_video_stream->codec;
  370.  ret = av_image_alloc(video_dst_data, video_dst_linesize,
  371.  video_dec_ctx->width, video_dec_ctx->height,
  372.  video_dec_ctx->pix_fmt, 1);
  373. if (ret < 0) {
  374.  fprintf(stderr, "Could not allocate raw video buffer\n");
  375. }
  376.  video_dst_bufsize = ret;
  377. }
  378.  input_frame = avcodec_alloc_frame();
  379. if (!input_frame) {
  380.  fprintf(stderr, "Could not allocate frame\n");
  381.  ret = AVERROR(ENOMEM);
  382. exit(-1);
  383. }
  384. /* allocate the output media context */
  385.  avformat_alloc_output_context2(&oc, NULL, NULL, filename);
  386. if (!oc) {
  387.  printf("Could not deduce output format from file extension: using MPEG.\n");
  388.  avformat_alloc_output_context2(&oc, NULL, "mpeg", filename);
  389. }
  390. if (!oc) {
  391.  return 1;
  392. }
  393.  fmt = oc->oformat;
  394.  video_st = NULL;
  395.  audio_st = NULL;
  396.  fmt->video_codec = AV_CODEC_ID_H264;
  397. if (fmt->video_codec != AV_CODEC_ID_NONE) {
  398.  video_st = add_stream(oc, &video_codec, AV_CODEC_ID_H264);
  399. }
  400. if (video_st->codec) {
  401.  video_st->codec->width = video_dec_ctx->width;
  402.  video_st->codec->height = video_dec_ctx->height;
  403. }
  404.  fmt->audio_codec = AV_CODEC_ID_MP3;
  405. if (fmt->audio_codec != AV_CODEC_ID_NONE) {
  406.  audio_st = add_stream(oc, &audio_codec, AV_CODEC_ID_MP3);
  407. }
  408. /* Now that all the parameters are set, we can open the audio and
  409. * video codecs and allocate the necessary encode buffers. */
  410. if (video_st)
  411.  open_video(oc, video_codec, video_st);
  412. if (audio_st)
  413.  open_audio(oc, audio_codec, audio_st);
  414.  av_dump_format(oc, 0, filename, 1);
  415. /* open the output file, if needed */
  416. if (!(fmt->flags & AVFMT_NOFILE)) {
  417.  ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);
  418. if (ret < 0) {
  419.  fprintf(stderr, "Could not open '%s': %s\n", filename,
  420.  av_err2str(ret));
  421.  return 1;
  422. }
  423. }
  424. /* Write the stream header, if any. */
  425.  ret = avformat_write_header(oc, NULL);
  426. if (ret < 0) {
  427.  fprintf(stderr, "Error occurred when opening output file: %s\n",
  428.  av_err2str(ret));
  429.  return 1;
  430. }
  431.  av_init_packet(&input_pkt);
  432.  input_pkt.data = NULL;
  433.  input_pkt.size = 0;
  434. if (frame)
  435.  frame->pts = 0;
  436. for (;;) {
  437. /* Compute current audio and video time. */
  438.  audio_time = audio_st ? audio_st->pts.val * av_q2d(audio_st->time_base) : 0.0;
  439.  video_time = video_st ? video_st->pts.val * av_q2d(video_st->time_base) : 0.0;
  440. if ((!audio_st || audio_time >= STREAM_DURATION) &&
  441. (!video_st || video_time >= STREAM_DURATION))
  442.  break;
  443. /* write interleaved audio and video frames */
  444. if (!video_st || (video_st && audio_st && audio_time < video_time)) {
  445.  write_audio_frame(oc, audio_st);
  446. } else {
  447.  av_read_frame(input_fmt_ctx, &input_pkt);
  448.  decoded = input_pkt.size;
  449. if (input_pkt.stream_index == video_stream_idx) {
  450. /* decode video frame */
  451.  ret = avcodec_decode_video2(video_dec_ctx, input_frame, &got_frame, &input_pkt);
  452. if (ret < 0) {
  453.  fprintf(stderr, "Error decoding video frame\n");
  454.  return ret;
  455. }
  456. if (got_frame) {
  457.  av_image_copy(&dst_picture, video_dst_linesize,
  458. (const uint8_t **)(input_frame->data), input_frame->linesize,
  459.  video_dec_ctx->pix_fmt, video_dec_ctx->width, video_dec_ctx->height);
  460. }
  461. }
  462.  write_video_frame(oc, video_st);
  463.  frame->pts += av_rescale_q(1, video_st->codec->time_base, video_st->time_base);
  464. }
  465. }
  466.  av_write_trailer(oc);
  467. /* Close each codec. */
  468. if (video_st)
  469.  close_video(oc, video_st);
  470. if (audio_st)
  471.  close_audio(oc, audio_st);
  472. if (!(fmt->flags & AVFMT_NOFILE))
  473.  avio_close(oc->pb);
  474.  avformat_free_context(oc);
  475.  av_free(input_frame);
  476.  av_free(video_dst_data[0]);
  477.  avcodec_close(video_dec_ctx);
  478.  return 0;
  479. }

以上代码为从dox/example/muxing.c中修改得到

编译命令如下:

点击(此处)折叠或打开

  1. gcc -g doc/examples/muxing.c -o muxing -lavcodec -lavdevice -lavfilter -lavformat -lavutil -lswscale -lswresample -lpostproc -lx264 -lmp3lame -lz -liconv -lbz2

执行命令如下:

点击(此处)折叠或打开

  1. ./muxing output.mp4 ~/Movies/input.avi

执行后效果如下:

查看转码完成后的多媒体文件的信息:

查看转码后的文件的视频:

本文参与 腾讯云自媒体分享计划,分享自作者个人站点/博客。
原始发表:2013-10-03 ,如有侵权请联系 cloudcommunity@tencent.com 删除

本文分享自 作者个人站点/博客 前往查看

如有侵权,请联系 cloudcommunity@tencent.com 删除。

本文参与 腾讯云自媒体分享计划  ,欢迎热爱写作的你一起参与!

评论
登录后参与评论
0 条评论
热度
最新
推荐阅读
领券
问题归档专栏文章快讯文章归档关键词归档开发者手册归档开发者手册 Section 归档