simple_decoder

00001 /*
00002  *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
00003  *
00004  *  Use of this source code is governed by a BSD-style license
00005  *  that can be found in the LICENSE file in the root of the source
00006  *  tree. An additional intellectual property rights grant can be found
00007  *  in the file PATENTS.  All contributing project authors may
00008  *  be found in the AUTHORS file in the root of the source tree.
00009  */
00010 
00011 // Simple Decoder
00012 // ==============
00013 //
00014 // This is an example of a simple decoder loop. It takes an input file
00015 // containing the compressed data (in IVF format), passes it through the
00016 // decoder, and writes the decompressed frames to disk. Other decoder
00017 // examples build upon this one.
00018 //
00019 // The details of the IVF format have been elided from this example for
00020 // simplicity of presentation, as IVF files will not generally be used by
00021 // your application. In general, an IVF file consists of a file header,
00022 // followed by a variable number of frames. Each frame consists of a frame
00023 // header followed by a variable length payload. The length of the payload
00024 // is specified in the first four bytes of the frame header. The payload is
00025 // the raw compressed data.
00026 //
00027 // Standard Includes
00028 // -----------------
00029 // For decoders, you only have to include `vpx_decoder.h` and then any
00030 // header files for the specific codecs you use. In this case, we're using
00031 // vp8.
00032 //
00033 // Initializing The Codec
00034 // ----------------------
00035 // The libvpx decoder is initialized by the call to vpx_codec_dec_init().
00036 // Determining the codec interface to use is handled by VpxVideoReader and the
00037 // functions prefixed with vpx_video_reader_. Discussion of those functions is
00038 // beyond the scope of this example, but the main gist is to open the input file
00039 // and parse just enough of it to determine if it's a VPx file and which VPx
00040 // codec is contained within the file.
00041 // Note the NULL pointer passed to vpx_codec_dec_init(). We do that in this
00042 // example because we want the algorithm to determine the stream configuration
00043 // (width/height) and allocate memory automatically.
00044 //
00045 // Decoding A Frame
00046 // ----------------
00047 // Once the frame has been read into memory, it is decoded using the
00048 // `vpx_codec_decode` function. The call takes a pointer to the data
00049 // (`frame`) and the length of the data (`frame_size`). No application data
00050 // is associated with the frame in this example, so the `user_priv`
00051 // parameter is NULL. The `deadline` parameter is left at zero for this
00052 // example. This parameter is generally only used when doing adaptive post
00053 // processing.
00054 //
00055 // Codecs may produce a variable number of output frames for every call to
00056 // `vpx_codec_decode`. These frames are retrieved by the
00057 // `vpx_codec_get_frame` iterator function. The iterator variable `iter` is
00058 // initialized to NULL each time `vpx_codec_decode` is called.
00059 // `vpx_codec_get_frame` is called in a loop, returning a pointer to a
00060 // decoded image or NULL to indicate the end of list.
00061 //
00062 // Processing The Decoded Data
00063 // ---------------------------
00064 // In this example, we simply write the encoded data to disk. It is
00065 // important to honor the image's `stride` values.
00066 //
00067 // Cleanup
00068 // -------
00069 // The `vpx_codec_destroy` call frees any memory allocated by the codec.
00070 //
00071 // Error Handling
00072 // --------------
00073 // This example does not special case any error return codes. If there was
00074 // an error, a descriptive message is printed and the program exits. With
00075 // few exceptions, vpx_codec functions return an enumerated error status,
00076 // with the value `0` indicating success.
00077 
00078 #include <stdio.h>
00079 #include <stdlib.h>
00080 #include <string.h>
00081 
00082 #include "vpx/vpx_decoder.h"
00083 
00084 #include "../tools_common.h"
00085 #include "../video_reader.h"
00086 #include "./vpx_config.h"
00087 
00088 static const char *exec_name;
00089 
00090 void usage_exit(void) {
00091   fprintf(stderr, "Usage: %s <infile> <outfile>\n", exec_name);
00092   exit(EXIT_FAILURE);
00093 }
00094 
00095 int main(int argc, char **argv) {
00096   int frame_cnt = 0;
00097   FILE *outfile = NULL;
00098   vpx_codec_ctx_t codec;
00099   VpxVideoReader *reader = NULL;
00100   const VpxInterface *decoder = NULL;
00101   const VpxVideoInfo *info = NULL;
00102 
00103   exec_name = argv[0];
00104 
00105   if (argc != 3) die("Invalid number of arguments.");
00106 
00107   reader = vpx_video_reader_open(argv[1]);
00108   if (!reader) die("Failed to open %s for reading.", argv[1]);
00109 
00110   if (!(outfile = fopen(argv[2], "wb")))
00111     die("Failed to open %s for writing.", argv[2]);
00112 
00113   info = vpx_video_reader_get_info(reader);
00114 
00115   decoder = get_vpx_decoder_by_fourcc(info->codec_fourcc);
00116   if (!decoder) die("Unknown input codec.");
00117 
00118   printf("Using %s\n", vpx_codec_iface_name(decoder->codec_interface()));
00119 
00120   if (vpx_codec_dec_init(&codec, decoder->codec_interface(), NULL, 0))
00121     die_codec(&codec, "Failed to initialize decoder.");
00122 
00123   while (vpx_video_reader_read_frame(reader)) {
00124     vpx_codec_iter_t iter = NULL;
00125     vpx_image_t *img = NULL;
00126     size_t frame_size = 0;
00127     const unsigned char *frame =
00128         vpx_video_reader_get_frame(reader, &frame_size);
00129     if (vpx_codec_decode(&codec, frame, (unsigned int)frame_size, NULL, 0))
00130       die_codec(&codec, "Failed to decode frame.");
00131 
00132     while ((img = vpx_codec_get_frame(&codec, &iter)) != NULL) {
00133       vpx_img_write(img, outfile);
00134       ++frame_cnt;
00135     }
00136   }
00137 
00138   printf("Processed %d frames.\n", frame_cnt);
00139   if (vpx_codec_destroy(&codec)) die_codec(&codec, "Failed to destroy codec");
00140 
00141   printf("Play: ffplay -f rawvideo -pix_fmt yuv420p -s %dx%d %s\n",
00142          info->frame_width, info->frame_height, argv[2]);
00143 
00144   vpx_video_reader_close(reader);
00145 
00146   fclose(outfile);
00147 
00148   return EXIT_SUCCESS;
00149 }

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