examples/simple_decoder.c

   1 /*
   2  *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
   3  *
   4  *  Use of this source code is governed by a BSD-style license
   5  *  that can be found in the LICENSE file in the root of the source
   6  *  tree. An additional intellectual property rights grant can be found
   7  *  in the file PATENTS.  All contributing project authors may
   8  *  be found in the AUTHORS file in the root of the source tree.
   9  */
  10
  11
  12 // Simple Decoder
  13 // ==============
  14 //
  15 // This is an example of a simple decoder loop. It takes an input file
  16 // containing the compressed data (in IVF format), passes it through the
  17 // decoder, and writes the decompressed frames to disk. Other decoder
  18 // examples build upon this one.
  19 //
  20 // The details of the IVF format have been elided from this example for
  21 // simplicity of presentation, as IVF files will not generally be used by
  22 // your application. In general, an IVF file consists of a file header,
  23 // followed by a variable number of frames. Each frame consists of a frame
  24 // header followed by a variable length payload. The length of the payload
  25 // is specified in the first four bytes of the frame header. The payload is
  26 // the raw compressed data.
  27 //
  28 // Standard Includes
  29 // -----------------
  30 // For decoders, you only have to include `vpx_decoder.h` and then any
  31 // header files for the specific codecs you use. In this case, we're using
  32 // vp8.
  33 //
  34 // Initializing The Codec
  35 // ----------------------
  36 // The libvpx decoder is initialized by the call to vpx_codec_dec_init().
  37 // Determining the codec interface to use is handled by VpxVideoReader and the
  38 // functions prefixed with vpx_video_reader_. Discussion of those functions is
  39 // beyond the scope of this example, but the main gist is to open the input file
  40 // and parse just enough of it to determine if it's a VPx file and which VPx
  41 // codec is contained within the file.
  42 // Note the NULL pointer passed to vpx_codec_dec_init(). We do that in this
  43 // example because we want the algorithm to determine the stream configuration
  44 // (width/height) and allocate memory automatically.
  45 //
  46 // Decoding A Frame
  47 // ----------------
  48 // Once the frame has been read into memory, it is decoded using the
  49 // `vpx_codec_decode` function. The call takes a pointer to the data
  50 // (`frame`) and the length of the data (`frame_size`). No application data
  51 // is associated with the frame in this example, so the `user_priv`
  52 // parameter is NULL. The `deadline` parameter is left at zero for this
  53 // example. This parameter is generally only used when doing adaptive post
  54 // processing.
  55 //
  56 // Codecs may produce a variable number of output frames for every call to
  57 // `vpx_codec_decode`. These frames are retrieved by the
  58 // `vpx_codec_get_frame` iterator function. The iterator variable `iter` is
  59 // initialized to NULL each time `vpx_codec_decode` is called.
  60 // `vpx_codec_get_frame` is called in a loop, returning a pointer to a
  61 // decoded image or NULL to indicate the end of list.
  62 //
  63 // Processing The Decoded Data
  64 // ---------------------------
  65 // In this example, we simply write the encoded data to disk. It is
  66 // important to honor the image's `stride` values.
  67 //
  68 // Cleanup
  69 // -------
  70 // The `vpx_codec_destroy` call frees any memory allocated by the codec.
  71 //
  72 // Error Handling
  73 // --------------
  74 // This example does not special case any error return codes. If there was
  75 // an error, a descriptive message is printed and the program exits. With
  76 // few exceptions, vpx_codec functions return an enumerated error status,
  77 // with the value `0` indicating success.
  78
  79 #include <stdio.h>
  80 #include <stdlib.h>
  81 #include <string.h>
  82
  83 #include "vpx/vpx_decoder.h"
  84
  85 #include "../tools_common.h"
  86 #include "../video_reader.h"
  87 #include "./vpx_config.h"
  88
  89 static const char *exec_name;
  90
  91 void usage_exit(void) {
  92   fprintf(stderr, "Usage: %s <infile> <outfile>\n", exec_name);
  93   exit(EXIT_FAILURE);
  94 }
  95
  96 int main(int argc, char **argv) {
  97   int frame_cnt = 0;
  98   FILE *outfile = NULL;
  99   vpx_codec_ctx_t codec;
 100   VpxVideoReader *reader = NULL;
 101   const VpxInterface *decoder = NULL;
 102   const VpxVideoInfo *info = NULL;
 103
 104   exec_name = argv[0];
 105
 106   if (argc != 3)
 107     die("Invalid number of arguments.");
 108
 109   reader = vpx_video_reader_open(argv[1]);
 110   if (!reader)
 111     die("Failed to open %s for reading.", argv[1]);
 112
 113   if (!(outfile = fopen(argv[2], "wb")))
 114     die("Failed to open %s for writing.", argv[2]);
 115
 116   info = vpx_video_reader_get_info(reader);
 117
 118   decoder = get_vpx_decoder_by_fourcc(info->codec_fourcc);
 119   if (!decoder)
 120     die("Unknown input codec.");
 121
 122   printf("Using %s\n", vpx_codec_iface_name(decoder->codec_interface()));
 123
 124   if (vpx_codec_dec_init(&codec, decoder->codec_interface(), NULL, 0))
 125     die_codec(&codec, "Failed to initialize decoder.");
 126
 127   while (vpx_video_reader_read_frame(reader)) {
 128     vpx_codec_iter_t iter = NULL;
 129     vpx_image_t *img = NULL;
 130     size_t frame_size = 0;
 131     const unsigned char *frame = vpx_video_reader_get_frame(reader,
 132                                                             &frame_size);
 133     if (vpx_codec_decode(&codec, frame, (unsigned int)frame_size, NULL, 0))
 134       die_codec(&codec, "Failed to decode frame.");
 135
 136     while ((img = vpx_codec_get_frame(&codec, &iter)) != NULL) {
 137       vpx_img_write(img, outfile);
 138       ++frame_cnt;
 139     }
 140   }
 141
 142   printf("Processed %d frames.\n", frame_cnt);
 143   if (vpx_codec_destroy(&codec))
 144     die_codec(&codec, "Failed to destroy codec");
 145
 146   printf("Play: ffplay -f rawvideo -pix_fmt yuv420p -s %dx%d %s\n",
 147          info->frame_width, info->frame_height, argv[2]);
 148
 149   vpx_video_reader_close(reader);
 150
 151   fclose(outfile);
 152
 153   return EXIT_SUCCESS;
 154 }