text: /*
   * Copyright (c) 2003 Fabrice Bellard
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
   * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  
  /**
   * @file
   * libavformat API example.
   *
   * @example output.c
   * Output a media file in any supported libavformat format. The default
   * codecs are used.
   */
  
  #include <stdlib.h>
  #include <stdio.h>
  #include <string.h>
  #include <math.h>
  
  #include "libavutil/channel_layout.h"
  #include "libavutil/mathematics.h"
  #include "libavutil/opt.h"
  #include "libavformat/avformat.h"
  #include "libavresample/avresample.h"
  #include "libswscale/swscale.h"
  
  /* 5 seconds stream duration */
  #define STREAM_DURATION   5.0
  #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 */
  
  #define SCALE_FLAGS SWS_BICUBIC
  
  // a wrapper around a single output AVStream
  typedef struct OutputStream {
      AVStream *st;
      AVCodecContext *enc;
  
      /* pts of the next frame that will be generated */
      int64_t next_pts;
  
      AVFrame *frame;
      AVFrame *tmp_frame;
  
      float t, tincr, tincr2;
  
      struct SwsContext *sws_ctx;
      AVAudioResampleContext *avr;
  } OutputStream;
  
  /**************************************************************/
  /* audio output */
  
  /*
   * add an audio output stream
   */
  static void add_audio_stream(OutputStream *ost, AVFormatContext *oc,
                               enum AVCodecID codec_id)
  {
      AVCodecContext *c;
      AVCodec *codec;
      int ret;
  
      /* find the audio encoder */
      codec = avcodec_find_encoder(codec_id);
      if (!codec) {
          fprintf(stderr, "codec not found\n");
          exit(1);
      }
  
      ost->st = avformat_new_stream(oc, NULL);
      if (!ost->st) {
          fprintf(stderr, "Could not alloc stream\n");
          exit(1);
      }
  
      c = avcodec_alloc_context3(codec);
      if (!c) {
          fprintf(stderr, "Could not alloc an encoding context\n");
          exit(1);
      }
      ost->enc = c;
  
      /* put sample parameters */
      c->sample_fmt     = codec->sample_fmts           ? codec->sample_fmts[0]           : AV_SAMPLE_FMT_S16;
      c->sample_rate    = codec->supported_samplerates ? codec->supported_samplerates[0] : 44100;
      c->channel_layout = codec->channel_layouts       ? codec->channel_layouts[0]       : AV_CH_LAYOUT_STEREO;
      c->channels       = av_get_channel_layout_nb_channels(c->channel_layout);
      c->bit_rate       = 64000;
  
      ost->st->time_base = (AVRational){ 1, c->sample_rate };
  
      // some formats want stream headers to be separate
      if (oc->oformat->flags & AVFMT_GLOBALHEADER)
          c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  
      /* initialize sample format conversion;
       * to simplify the code, we always pass the data through lavr, even
       * if the encoder supports the generated format directly -- the price is
       * some extra data copying;
       */
      ost->avr = avresample_alloc_context();
      if (!ost->avr) {
          fprintf(stderr, "Error allocating the resampling context\n");
          exit(1);
      }
  
      av_opt_set_int(ost->avr, "in_sample_fmt",      AV_SAMPLE_FMT_S16,   0);
      av_opt_set_int(ost->avr, "in_sample_rate",     44100,               0);
      av_opt_set_int(ost->avr, "in_channel_layout",  AV_CH_LAYOUT_STEREO, 0);
      av_opt_set_int(ost->avr, "out_sample_fmt",     c->sample_fmt,       0);
      av_opt_set_int(ost->avr, "out_sample_rate",    c->sample_rate,      0);
      av_opt_set_int(ost->avr, "out_channel_layout", c->channel_layout,   0);
  
      ret = avresample_open(ost->avr);
      if (ret < 0) {
          fprintf(stderr, "Error opening the resampling context\n");
          exit(1);
      }
  }
  
  static AVFrame *alloc_audio_frame(enum AVSampleFormat sample_fmt,
                                    uint64_t channel_layout,
                                    int sample_rate, int nb_samples)
  {
      AVFrame *frame = av_frame_alloc();
      int ret;
  
      if (!frame) {
          fprintf(stderr, "Error allocating an audio frame\n");
          exit(1);
      }
  
      frame->format = sample_fmt;
      frame->channel_layout = channel_layout;
      frame->sample_rate = sample_rate;
      frame->nb_samples = nb_samples;
  
      if (nb_samples) {
          ret = av_frame_get_buffer(frame, 0);
          if (ret < 0) {
              fprintf(stderr, "Error allocating an audio buffer\n");
              exit(1);
          }
      }
  
      return frame;
  }
  
  static void open_audio(AVFormatContext *oc, OutputStream *ost)
  {
      AVCodecContext *c;
      int nb_samples, ret;
  
      c = ost->enc;
  
      /* open it */
      if (avcodec_open2(c, NULL, NULL) < 0) {
          fprintf(stderr, "could not open codec\n");
          exit(1);
      }
  
      /* init signal generator */
      ost->t     = 0;
      ost->tincr = 2 * M_PI * 110.0 / c->sample_rate;
      /* increment frequency by 110 Hz per second */
      ost->tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
  
      if (c->codec->capabilities & AV_CODEC_CAP_VARIABLE_FRAME_SIZE)
          nb_samples = 10000;
      else
          nb_samples = c->frame_size;
  
      ost->frame     = alloc_audio_frame(c->sample_fmt, c->channel_layout,
                                         c->sample_rate, nb_samples);
      ost->tmp_frame = alloc_audio_frame(AV_SAMPLE_FMT_S16, AV_CH_LAYOUT_STEREO,
                                         44100, nb_samples);
  
      /* copy the stream parameters to the muxer */
      ret = avcodec_parameters_from_context(ost->st->codecpar, c);
      if (ret < 0) {
          fprintf(stderr, "Could not copy the stream parameters\n");
          exit(1);
      }
  }
  
  /* Prepare a 16 bit dummy audio frame of 'frame_size' samples and
   * 'nb_channels' channels. */
  static AVFrame *get_audio_frame(OutputStream *ost)
  {
      AVFrame *frame = ost->tmp_frame;
      int j, i, v;
      int16_t *q = (int16_t*)frame->data[0];
  
      /* check if we want to generate more frames */
      if (av_compare_ts(ost->next_pts, ost->enc->time_base,
                        STREAM_DURATION, (AVRational){ 1, 1 }) >= 0)
          return NULL;
  
  
      for (j = 0; j < frame->nb_samples; j++) {
          v = (int)(sin(ost->t) * 10000);
          for (i = 0; i < ost->enc->channels; i++)
              *q++ = v;
          ost->t     += ost->tincr;
          ost->tincr += ost->tincr2;
      }
  
      return frame;
  }
  
  /* if a frame is provided, send it to the encoder, otherwise flush the encoder;
   * return 1 when encoding is finished, 0 otherwise
   */
  static int encode_audio_frame(AVFormatContext *oc, OutputStream *ost,
                                AVFrame *frame)
  {
      AVPacket pkt = { 0 }; // data and size must be 0;
      int got_packet;
  
      av_init_packet(&pkt);
      avcodec_encode_audio2(ost->enc, &pkt, frame, &got_packet);
  
      if (got_packet) {
          pkt.stream_index = ost->st->index;
  
          av_packet_rescale_ts(&pkt, ost->enc->time_base, ost->st->time_base);
  
          /* Write the compressed frame to the media file. */
          if (av_interleaved_write_frame(oc, &pkt) != 0) {
              fprintf(stderr, "Error while writing audio frame\n");
              exit(1);
          }
      }
  
      return (frame || got_packet) ? 0 : 1;
  }
  
  /*
   * encode one audio frame and send it to the muxer
   * return 1 when encoding is finished, 0 otherwise
   */
  static int process_audio_stream(AVFormatContext *oc, OutputStream *ost)
  {
      AVFrame *frame;
      int got_output = 0;
      int ret;
  
      frame = get_audio_frame(ost);
      got_output |= !!frame;
  
      /* feed the data to lavr */
      if (frame) {
          ret = avresample_convert(ost->avr, NULL, 0, 0,
                                   frame->extended_data, frame->linesize[0],
                                   frame->nb_samples);
          if (ret < 0) {
              fprintf(stderr, "Error feeding audio data to the resampler\n");
              exit(1);
          }
      }
  
      while ((frame && avresample_available(ost->avr) >= ost->frame->nb_samples) ||
             (!frame && avresample_get_out_samples(ost->avr, 0))) {
          /* when we pass a frame to the encoder, it may keep a reference to it
           * internally;
           * make sure we do not overwrite it here
           */
          ret = av_frame_make_writable(ost->frame);
          if (ret < 0)
              exit(1);
  
          /* the difference between the two avresample calls here is that the
           * first one just reads the already converted data that is buffered in
           * the lavr output buffer, while the second one also flushes the
           * resampler */
          if (frame) {
              ret = avresample_read(ost->avr, ost->frame->extended_data,
                                    ost->frame->nb_samples);
          } else {
              ret = avresample_convert(ost->avr, ost->frame->extended_data,
                                       ost->frame->linesize[0], ost->frame->nb_samples,
                                       NULL, 0, 0);
          }
  
          if (ret < 0) {
              fprintf(stderr, "Error while resampling\n");
              exit(1);
          } else if (frame && ret != ost->frame->nb_samples) {
              fprintf(stderr, "Too few samples returned from lavr\n");
              exit(1);
          }
  
          ost->frame->nb_samples = ret;
  
          ost->frame->pts        = ost->next_pts;
          ost->next_pts         += ost->frame->nb_samples;
  
          got_output |= encode_audio_frame(oc, ost, ret ? ost->frame : NULL);
      }
  
      return !got_output;
  }
  
  /**************************************************************/
  /* video output */
  
  /* Add a video output stream. */
  static void add_video_stream(OutputStream *ost, AVFormatContext *oc,
                               enum AVCodecID codec_id)
  {
      AVCodecContext *c;
      AVCodec *codec;
  
      /* find the video encoder */
      codec = avcodec_find_encoder(codec_id);
      if (!codec) {
          fprintf(stderr, "codec not found\n");
          exit(1);
      }
  
      ost->st = avformat_new_stream(oc, NULL);
      if (!ost->st) {
          fprintf(stderr, "Could not alloc stream\n");
          exit(1);
      }
  
      c = avcodec_alloc_context3(codec);
      if (!c) {
          fprintf(stderr, "Could not alloc an encoding context\n");
          exit(1);
      }
      ost->enc = c;
  
      /* Put sample parameters. */
      c->bit_rate = 400000;
      /* Resolution must be a multiple of two. */
      c->width    = 352;
      c->height   = 288;
      /* timebase: This is the fundamental unit of time (in seconds) in terms
       * of which frame timestamps are represented. For fixed-fps content,
       * timebase should be 1/framerate and timestamp increments should be
       * identical to 1. */
      ost->st->time_base = (AVRational){ 1, STREAM_FRAME_RATE };
      c->time_base       = ost->st->time_base;
  
      c->gop_size      = 12; /* emit one intra frame every twelve frames at most */
      c->pix_fmt       = STREAM_PIX_FMT;
      if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
          /* just for testing, we also add B-frames */
          c->max_b_frames = 2;
      }
      if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
          /* Needed to avoid using macroblocks in which some coeffs overflow.
           * This does not happen with normal video, it just happens here as
           * the motion of the chroma plane does not match the luma plane. */
          c->mb_decision = 2;
      }
      /* Some formats want stream headers to be separate. */
      if (oc->oformat->flags & AVFMT_GLOBALHEADER)
          c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  }
  
  static AVFrame *alloc_picture(enum AVPixelFormat pix_fmt, int width, int height)
  {
      AVFrame *picture;
      int ret;
  
      picture = av_frame_alloc();
      if (!picture)
          return NULL;
  
      picture->format = pix_fmt;
      picture->width  = width;
      picture->height = height;
  
      /* allocate the buffers for the frame data */
      ret = av_frame_get_buffer(picture, 32);
      if (ret < 0) {
          fprintf(stderr, "Could not allocate frame data.\n");
          exit(1);
      }
  
      return picture;
  }
  
  static void open_video(AVFormatContext *oc, OutputStream *ost)
  {
      AVCodecContext *c;
      int ret;
  
      c = ost->enc;
  
      /* open the codec */
      if (avcodec_open2(c, NULL, NULL) < 0) {
          fprintf(stderr, "could not open codec\n");
          exit(1);
      }
  
      /* Allocate the encoded raw picture. */
      ost->frame = alloc_picture(c->pix_fmt, c->width, c->height);
      if (!ost->frame) {
          fprintf(stderr, "Could not allocate picture\n");
          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. */
      ost->tmp_frame = NULL;
      if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
          ost->tmp_frame = alloc_picture(AV_PIX_FMT_YUV420P, c->width, c->height);
          if (!ost->tmp_frame) {
              fprintf(stderr, "Could not allocate temporary picture\n");
              exit(1);
          }
      }
  
      /* copy the stream parameters to the muxer */
      ret = avcodec_parameters_from_context(ost->st->codecpar, c);
      if (ret < 0) {
          fprintf(stderr, "Could not copy the stream parameters\n");
          exit(1);
      }
  }
  
  /* Prepare a dummy image. */
  static void fill_yuv_image(AVFrame *pict, int frame_index,
                             int width, int height)
  {
      int x, y, i, ret;
  
      /* when we pass a frame to the encoder, it may keep a reference to it
       * internally;
       * make sure we do not overwrite it here
       */
      ret = av_frame_make_writable(pict);
      if (ret < 0)
          exit(1);
  
      i = frame_index;
  
      /* Y */
      for (y = 0; y < height; y++)
          for (x = 0; x < width; x++)
              pict->data[0][y * pict->linesize[0] + x] = x + y + i * 3;
  
      /* Cb and Cr */
      for (y = 0; y < height / 2; y++) {
          for (x = 0; x < width / 2; x++) {
              pict->data[1][y * pict->linesize[1] + x] = 128 + y + i * 2;
              pict->data[2][y * pict->linesize[2] + x] = 64 + x + i * 5;
          }
      }
  }
  
  static AVFrame *get_video_frame(OutputStream *ost)
  {
      AVCodecContext *c = ost->enc;
  
      /* check if we want to generate more frames */
      if (av_compare_ts(ost->next_pts, c->time_base,
                        STREAM_DURATION, (AVRational){ 1, 1 }) >= 0)
          return NULL;
  
      if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
          /* as we only generate a YUV420P picture, we must convert it
           * to the codec pixel format if needed */
          if (!ost->sws_ctx) {
              ost->sws_ctx = sws_getContext(c->width, c->height,
                                            AV_PIX_FMT_YUV420P,
                                            c->width, c->height,
                                            c->pix_fmt,
                                            SCALE_FLAGS, NULL, NULL, NULL);
              if (!ost->sws_ctx) {
                  fprintf(stderr,
                          "Cannot initialize the conversion context\n");
                  exit(1);
              }
          }
          fill_yuv_image(ost->tmp_frame, ost->next_pts, c->width, c->height);
          sws_scale(ost->sws_ctx, ost->tmp_frame->data, ost->tmp_frame->linesize,
                    0, c->height, ost->frame->data, ost->frame->linesize);
      } else {
          fill_yuv_image(ost->frame, ost->next_pts, c->width, c->height);
      }
  
      ost->frame->pts = ost->next_pts++;
  
      return ost->frame;
  }
  
  /*
   * encode one video frame and send it to the muxer
   * return 1 when encoding is finished, 0 otherwise
   */
  static int write_video_frame(AVFormatContext *oc, OutputStream *ost)
  {
      int ret;
      AVCodecContext *c;
      AVFrame *frame;
      AVPacket pkt   = { 0 };
      int got_packet = 0;
  
      c = ost->enc;
  
      frame = get_video_frame(ost);
  
      av_init_packet(&pkt);
  
      /* encode the image */
      ret = avcodec_encode_video2(c, &pkt, frame, &got_packet);
      if (ret < 0) {
          fprintf(stderr, "Error encoding a video frame\n");
          exit(1);
      }
  
      if (got_packet) {
          av_packet_rescale_ts(&pkt, c->time_base, ost->st->time_base);
          pkt.stream_index = ost->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 video frame\n");
          exit(1);
      }
  
      return (frame || got_packet) ? 0 : 1;
  }
  
  static void close_stream(AVFormatContext *oc, OutputStream *ost)
  {
      avcodec_free_context(&ost->enc);
      av_frame_free(&ost->frame);
      av_frame_free(&ost->tmp_frame);
      sws_freeContext(ost->sws_ctx);
      avresample_free(&ost->avr);
  }
  
  /**************************************************************/
  /* media file output */
  
  int main(int argc, char **argv)
  {
      OutputStream video_st = { 0 }, audio_st = { 0 };
      const char *filename;
      AVOutputFormat *fmt;
      AVFormatContext *oc;
      int have_video = 0, have_audio = 0;
      int encode_video = 0, encode_audio = 0;
  
      /* Initialize libavcodec, and register all codecs and formats. */
      av_register_all();
  
      if (argc != 2) {
          printf("usage: %s output_file\n"
                 "API example program to output a media file with libavformat.\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;
      }
  
      filename = argv[1];
  
      /* Autodetect the output format from the name. default is MPEG. */
      fmt = av_guess_format(NULL, filename, NULL);
      if (!fmt) {
          printf("Could not deduce output format from file extension: using MPEG.\n");
          fmt = av_guess_format("mpeg", NULL, NULL);
      }
      if (!fmt) {
          fprintf(stderr, "Could not find suitable output format\n");
          return 1;
      }
  
      /* Allocate the output media context. */
      oc = avformat_alloc_context();
      if (!oc) {
          fprintf(stderr, "Memory error\n");
          return 1;
      }
      oc->oformat = fmt;
      snprintf(oc->filename, sizeof(oc->filename), "%s", filename);
  
      /* Add the audio and video streams using the default format codecs
       * and initialize the codecs. */
      if (fmt->video_codec != AV_CODEC_ID_NONE) {
          add_video_stream(&video_st, oc, fmt->video_codec);
          have_video = 1;
          encode_video = 1;
      }
      if (fmt->audio_codec != AV_CODEC_ID_NONE) {
          add_audio_stream(&audio_st, oc, fmt->audio_codec);
          have_audio = 1;
          encode_audio = 1;
      }
  
      /* Now that all the parameters are set, we can open the audio and
       * video codecs and allocate the necessary encode buffers. */
      if (have_video)
          open_video(oc, &video_st);
      if (have_audio)
          open_audio(oc, &audio_st);
  
      av_dump_format(oc, 0, filename, 1);
  
      /* open the output file, if needed */
      if (!(fmt->flags & AVFMT_NOFILE)) {
          if (avio_open(&oc->pb, filename, AVIO_FLAG_WRITE) < 0) {
              fprintf(stderr, "Could not open '%s'\n", filename);
              return 1;
          }
      }
  
      /* Write the stream header, if any. */
      avformat_write_header(oc, NULL);
  
      while (encode_video || encode_audio) {
          /* select the stream to encode */
          if (encode_video &&
              (!encode_audio || av_compare_ts(video_st.next_pts, video_st.enc->time_base,
                                              audio_st.next_pts, audio_st.enc->time_base) <= 0)) {
              encode_video = !write_video_frame(oc, &video_st);
          } else {
              encode_audio = !process_audio_stream(oc, &audio_st);
          }
      }
  
      /* Write the trailer, if any. The trailer must be written before you
       * close the CodecContexts open when you wrote the header; otherwise
       * av_write_trailer() may try to use memory that was freed on
       * av_codec_close(). */
      av_write_trailer(oc);
  
      /* Close each codec. */
      if (have_video)
          close_stream(oc, &video_st);
      if (have_audio)
          close_stream(oc, &audio_st);
  
      if (!(fmt->flags & AVFMT_NOFILE))
          /* Close the output file. */
          avio_close(oc->pb);
  
      /* free the stream */
      avformat_free_context(oc);
  
      return 0;
  }
  