doc/examples/demuxing_decoding.c - manifest_repos/ffmpeg - Git at Google

 /*
  * Copyright (c) 2012 Stefano Sabatini
  *
  * 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
  * Demuxing and decoding example.
  *
  * Show how to use the libavformat and libavcodec API to demux and
  * decode audio and video data.
  * @example demuxing_decoding.c
  */

 #include <libavutil/imgutils.h>
 #include <libavutil/samplefmt.h>
 #include <libavutil/timestamp.h>
 #include <libavformat/avformat.h>

 static AVFormatContext *fmt_ctx = NULL;
 static AVCodecContext *video_dec_ctx = NULL, *audio_dec_ctx;
 static int width, height;
 static enum AVPixelFormat pix_fmt;
 static AVStream *video_stream = NULL, *audio_stream = NULL;
 static const char *src_filename = NULL;
 static const char *video_dst_filename = NULL;
 static const char *audio_dst_filename = NULL;
 static FILE *video_dst_file = NULL;
 static FILE *audio_dst_file = NULL;

 static uint8_t *video_dst_data[4] = {NULL};
 static int      video_dst_linesize[4];
 static int video_dst_bufsize;

 static int video_stream_idx = -1, audio_stream_idx = -1;
 static AVFrame *frame = NULL;
 static AVPacket pkt;
 static int video_frame_count = 0;
 static int audio_frame_count = 0;

 static int output_video_frame(AVFrame *frame)
 {
     if (frame->width != width || frame->height != height ||
         frame->format != pix_fmt) {
         /* To handle this change, one could call av_image_alloc again and
          * decode the following frames into another rawvideo file. */
         fprintf(stderr, "Error: Width, height and pixel format have to be "
                 "constant in a rawvideo file, but the width, height or "
                 "pixel format of the input video changed:\n"
                 "old: width = %d, height = %d, format = %s\n"
                 "new: width = %d, height = %d, format = %s\n",
                 width, height, av_get_pix_fmt_name(pix_fmt),
                 frame->width, frame->height,
                 av_get_pix_fmt_name(frame->format));
         return -1;
     }

     printf("video_frame n:%d coded_n:%d\n",
            video_frame_count++, frame->coded_picture_number);

     /* copy decoded frame to destination buffer:
      * this is required since rawvideo expects non aligned data */
     av_image_copy(video_dst_data, video_dst_linesize,
                   (const uint8_t **)(frame->data), frame->linesize,
                   pix_fmt, width, height);

     /* write to rawvideo file */
     fwrite(video_dst_data[0], 1, video_dst_bufsize, video_dst_file);
     return 0;
 }

 static int output_audio_frame(AVFrame *frame)
 {
     size_t unpadded_linesize = frame->nb_samples * av_get_bytes_per_sample(frame->format);
     printf("audio_frame n:%d nb_samples:%d pts:%s\n",
            audio_frame_count++, frame->nb_samples,
            av_ts2timestr(frame->pts, &audio_dec_ctx->time_base));

     /* Write the raw audio data samples of the first plane. This works
      * fine for packed formats (e.g. AV_SAMPLE_FMT_S16). However,
      * most audio decoders output planar audio, which uses a separate
      * plane of audio samples for each channel (e.g. AV_SAMPLE_FMT_S16P).
      * In other words, this code will write only the first audio channel
      * in these cases.
      * You should use libswresample or libavfilter to convert the frame
      * to packed data. */
     fwrite(frame->extended_data[0], 1, unpadded_linesize, audio_dst_file);

     return 0;
 }

 static int decode_packet(AVCodecContext *dec, const AVPacket *pkt)
 {
     int ret = 0;

     // submit the packet to the decoder
     ret = avcodec_send_packet(dec, pkt);
     if (ret < 0) {
         fprintf(stderr, "Error submitting a packet for decoding (%s)\n", av_err2str(ret));
         return ret;
     }

     // get all the available frames from the decoder
     while (ret >= 0) {
         ret = avcodec_receive_frame(dec, frame);
         if (ret < 0) {
             // those two return values are special and mean there is no output
             // frame available, but there were no errors during decoding
             if (ret == AVERROR_EOF || ret == AVERROR(EAGAIN))
                 return 0;

             fprintf(stderr, "Error during decoding (%s)\n", av_err2str(ret));
             return ret;
         }

         // write the frame data to output file
         if (dec->codec->type == AVMEDIA_TYPE_VIDEO)
             ret = output_video_frame(frame);
         else
             ret = output_audio_frame(frame);

         av_frame_unref(frame);
         if (ret < 0)
             return ret;
     }

     return 0;
 }

 static int open_codec_context(int *stream_idx,
                               AVCodecContext **dec_ctx, AVFormatContext *fmt_ctx, enum AVMediaType type)
 {
     int ret, stream_index;
     AVStream *st;
     AVCodec *dec = NULL;
     AVDictionary *opts = NULL;

     ret = av_find_best_stream(fmt_ctx, type, -1, -1, NULL, 0);
     if (ret < 0) {
         fprintf(stderr, "Could not find %s stream in input file '%s'\n",
                 av_get_media_type_string(type), src_filename);
         return ret;
     } else {
         stream_index = ret;
         st = fmt_ctx->streams[stream_index];

         /* find decoder for the stream */
         dec = avcodec_find_decoder(st->codecpar->codec_id);
         if (!dec) {
             fprintf(stderr, "Failed to find %s codec\n",
                     av_get_media_type_string(type));
             return AVERROR(EINVAL);
         }

         /* Allocate a codec context for the decoder */
         *dec_ctx = avcodec_alloc_context3(dec);
         if (!*dec_ctx) {
             fprintf(stderr, "Failed to allocate the %s codec context\n",
                     av_get_media_type_string(type));
             return AVERROR(ENOMEM);
         }

         /* Copy codec parameters from input stream to output codec context */
         if ((ret = avcodec_parameters_to_context(*dec_ctx, st->codecpar)) < 0) {
             fprintf(stderr, "Failed to copy %s codec parameters to decoder context\n",
                     av_get_media_type_string(type));
             return ret;
         }

         /* Init the decoders */
         if ((ret = avcodec_open2(*dec_ctx, dec, &opts)) < 0) {
             fprintf(stderr, "Failed to open %s codec\n",
                     av_get_media_type_string(type));
             return ret;
         }
         *stream_idx = stream_index;
     }

     return 0;
 }

 static int get_format_from_sample_fmt(const char **fmt,
                                       enum AVSampleFormat sample_fmt)
 {
     int i;
     struct sample_fmt_entry {
         enum AVSampleFormat sample_fmt; const char *fmt_be, *fmt_le;
     } sample_fmt_entries[] = {
         { AV_SAMPLE_FMT_U8,  "u8",    "u8"    },
         { AV_SAMPLE_FMT_S16, "s16be", "s16le" },
         { AV_SAMPLE_FMT_S32, "s32be", "s32le" },
         { AV_SAMPLE_FMT_FLT, "f32be", "f32le" },
         { AV_SAMPLE_FMT_DBL, "f64be", "f64le" },
     };
     *fmt = NULL;

     for (i = 0; i < FF_ARRAY_ELEMS(sample_fmt_entries); i++) {
         struct sample_fmt_entry *entry = &sample_fmt_entries[i];
         if (sample_fmt == entry->sample_fmt) {
             *fmt = AV_NE(entry->fmt_be, entry->fmt_le);
             return 0;
         }
     }

     fprintf(stderr,
             "sample format %s is not supported as output format\n",
             av_get_sample_fmt_name(sample_fmt));
     return -1;
 }

 int main (int argc, char **argv)
 {
     int ret = 0;

     if (argc != 4) {
         fprintf(stderr, "usage: %s  input_file video_output_file audio_output_file\n"
                 "API example program to show how to read frames from an input file.\n"
                 "This program reads frames from a file, decodes them, and writes decoded\n"
                 "video frames to a rawvideo file named video_output_file, and decoded\n"
                 "audio frames to a rawaudio file named audio_output_file.\n",
                 argv[0]);
         exit(1);
     }
     src_filename = argv[1];
     video_dst_filename = argv[2];
     audio_dst_filename = argv[3];

     /* open input file, and allocate format context */
     if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0) {
         fprintf(stderr, "Could not open source file %s\n", src_filename);
         exit(1);
     }

     /* retrieve stream information */
     if (avformat_find_stream_info(fmt_ctx, NULL) < 0) {
         fprintf(stderr, "Could not find stream information\n");
         exit(1);
     }

     if (open_codec_context(&video_stream_idx, &video_dec_ctx, fmt_ctx, AVMEDIA_TYPE_VIDEO) >= 0) {
         video_stream = fmt_ctx->streams[video_stream_idx];

         video_dst_file = fopen(video_dst_filename, "wb");
         if (!video_dst_file) {
             fprintf(stderr, "Could not open destination file %s\n", video_dst_filename);
             ret = 1;
             goto end;
         }

         /* allocate image where the decoded image will be put */
         width = video_dec_ctx->width;
         height = video_dec_ctx->height;
         pix_fmt = video_dec_ctx->pix_fmt;
         ret = av_image_alloc(video_dst_data, video_dst_linesize,
                              width, height, pix_fmt, 1);
         if (ret < 0) {
             fprintf(stderr, "Could not allocate raw video buffer\n");
             goto end;
         }
         video_dst_bufsize = ret;
     }

     if (open_codec_context(&audio_stream_idx, &audio_dec_ctx, fmt_ctx, AVMEDIA_TYPE_AUDIO) >= 0) {
         audio_stream = fmt_ctx->streams[audio_stream_idx];
         audio_dst_file = fopen(audio_dst_filename, "wb");
         if (!audio_dst_file) {
             fprintf(stderr, "Could not open destination file %s\n", audio_dst_filename);
             ret = 1;
             goto end;
         }
     }

     /* dump input information to stderr */
     av_dump_format(fmt_ctx, 0, src_filename, 0);

     if (!audio_stream && !video_stream) {
         fprintf(stderr, "Could not find audio or video stream in the input, aborting\n");
         ret = 1;
         goto end;
     }

     frame = av_frame_alloc();
     if (!frame) {
         fprintf(stderr, "Could not allocate frame\n");
         ret = AVERROR(ENOMEM);
         goto end;
     }

     /* initialize packet, set data to NULL, let the demuxer fill it */
     av_init_packet(&pkt);
     pkt.data = NULL;
     pkt.size = 0;

     if (video_stream)
         printf("Demuxing video from file '%s' into '%s'\n", src_filename, video_dst_filename);
     if (audio_stream)
         printf("Demuxing audio from file '%s' into '%s'\n", src_filename, audio_dst_filename);

     /* read frames from the file */
     while (av_read_frame(fmt_ctx, &pkt) >= 0) {
         // check if the packet belongs to a stream we are interested in, otherwise
         // skip it
         if (pkt.stream_index == video_stream_idx)
             ret = decode_packet(video_dec_ctx, &pkt);
         else if (pkt.stream_index == audio_stream_idx)
             ret = decode_packet(audio_dec_ctx, &pkt);
         av_packet_unref(&pkt);
         if (ret < 0)
             break;
     }

     /* flush the decoders */
     if (video_dec_ctx)
         decode_packet(video_dec_ctx, NULL);
     if (audio_dec_ctx)
         decode_packet(audio_dec_ctx, NULL);

     printf("Demuxing succeeded.\n");

     if (video_stream) {
         printf("Play the output video file with the command:\n"
                "ffplay -f rawvideo -pix_fmt %s -video_size %dx%d %s\n",
                av_get_pix_fmt_name(pix_fmt), width, height,
                video_dst_filename);
     }

     if (audio_stream) {
         enum AVSampleFormat sfmt = audio_dec_ctx->sample_fmt;
         int n_channels = audio_dec_ctx->channels;
         const char *fmt;

         if (av_sample_fmt_is_planar(sfmt)) {
             const char *packed = av_get_sample_fmt_name(sfmt);
             printf("Warning: the sample format the decoder produced is planar "
                    "(%s). This example will output the first channel only.\n",
                    packed ? packed : "?");
             sfmt = av_get_packed_sample_fmt(sfmt);
             n_channels = 1;
         }

         if ((ret = get_format_from_sample_fmt(&fmt, sfmt)) < 0)
             goto end;

         printf("Play the output audio file with the command:\n"
                "ffplay -f %s -ac %d -ar %d %s\n",
                fmt, n_channels, audio_dec_ctx->sample_rate,
                audio_dst_filename);
     }

 end:
     avcodec_free_context(&video_dec_ctx);
     avcodec_free_context(&audio_dec_ctx);
     avformat_close_input(&fmt_ctx);
     if (video_dst_file)
         fclose(video_dst_file);
     if (audio_dst_file)
         fclose(audio_dst_file);
     av_frame_free(&frame);
     av_free(video_dst_data[0]);

     return ret < 0;
 }
	/*
	* Copyright (c) 2012 Stefano Sabatini
	*
	* 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
	* Demuxing and decoding example.
	*
	* Show how to use the libavformat and libavcodec API to demux and
	* decode audio and video data.
	* @example demuxing_decoding.c
	*/

	#include <libavutil/imgutils.h>
	#include <libavutil/samplefmt.h>
	#include <libavutil/timestamp.h>
	#include <libavformat/avformat.h>

	static AVFormatContext *fmt_ctx = NULL;
	static AVCodecContext video_dec_ctx = NULL, audio_dec_ctx;
	static int width, height;
	static enum AVPixelFormat pix_fmt;
	static AVStream video_stream = NULL, audio_stream = NULL;
	static const char *src_filename = NULL;
	static const char *video_dst_filename = NULL;
	static const char *audio_dst_filename = NULL;
	static FILE *video_dst_file = NULL;
	static FILE *audio_dst_file = NULL;

	static uint8_t *video_dst_data[4] = {NULL};
	static int video_dst_linesize[4];
	static int video_dst_bufsize;

	static int video_stream_idx = -1, audio_stream_idx = -1;
	static AVFrame *frame = NULL;
	static AVPacket pkt;
	static int video_frame_count = 0;
	static int audio_frame_count = 0;

	static int output_video_frame(AVFrame *frame)
	{
	if (frame->width != width \|\| frame->height != height \|\|
	frame->format != pix_fmt) {
	/* To handle this change, one could call av_image_alloc again and
	* decode the following frames into another rawvideo file. */
	fprintf(stderr, "Error: Width, height and pixel format have to be "
	"constant in a rawvideo file, but the width, height or "
	"pixel format of the input video changed:\n"
	"old: width = %d, height = %d, format = %s\n"
	"new: width = %d, height = %d, format = %s\n",
	width, height, av_get_pix_fmt_name(pix_fmt),
	frame->width, frame->height,
	av_get_pix_fmt_name(frame->format));
	return -1;
	}

	printf("video_frame n:%d coded_n:%d\n",
	video_frame_count++, frame->coded_picture_number);

	/* copy decoded frame to destination buffer:
	* this is required since rawvideo expects non aligned data */
	av_image_copy(video_dst_data, video_dst_linesize,
	(const uint8_t **)(frame->data), frame->linesize,
	pix_fmt, width, height);

	/* write to rawvideo file */
	fwrite(video_dst_data[0], 1, video_dst_bufsize, video_dst_file);
	return 0;
	}

	static int output_audio_frame(AVFrame *frame)
	{
	size_t unpadded_linesize = frame->nb_samples * av_get_bytes_per_sample(frame->format);
	printf("audio_frame n:%d nb_samples:%d pts:%s\n",
	audio_frame_count++, frame->nb_samples,
	av_ts2timestr(frame->pts, &audio_dec_ctx->time_base));

	/* Write the raw audio data samples of the first plane. This works
	* fine for packed formats (e.g. AV_SAMPLE_FMT_S16). However,
	* most audio decoders output planar audio, which uses a separate
	* plane of audio samples for each channel (e.g. AV_SAMPLE_FMT_S16P).
	* In other words, this code will write only the first audio channel
	* in these cases.
	* You should use libswresample or libavfilter to convert the frame
	* to packed data. */
	fwrite(frame->extended_data[0], 1, unpadded_linesize, audio_dst_file);

	return 0;
	}

	static int decode_packet(AVCodecContext dec, const AVPacket pkt)
	{
	int ret = 0;

	// submit the packet to the decoder
	ret = avcodec_send_packet(dec, pkt);
	if (ret < 0) {
	fprintf(stderr, "Error submitting a packet for decoding (%s)\n", av_err2str(ret));
	return ret;
	}

	// get all the available frames from the decoder
	while (ret >= 0) {
	ret = avcodec_receive_frame(dec, frame);
	if (ret < 0) {
	// those two return values are special and mean there is no output
	// frame available, but there were no errors during decoding
	if (ret == AVERROR_EOF \|\| ret == AVERROR(EAGAIN))
	return 0;

	fprintf(stderr, "Error during decoding (%s)\n", av_err2str(ret));
	return ret;
	}

	// write the frame data to output file
	if (dec->codec->type == AVMEDIA_TYPE_VIDEO)
	ret = output_video_frame(frame);
	else
	ret = output_audio_frame(frame);

	av_frame_unref(frame);
	if (ret < 0)
	return ret;
	}

	return 0;
	}

	static int open_codec_context(int *stream_idx,
	AVCodecContext *dec_ctx, AVFormatContext fmt_ctx, enum AVMediaType type)
	{
	int ret, stream_index;
	AVStream *st;
	AVCodec *dec = NULL;
	AVDictionary *opts = NULL;

	ret = av_find_best_stream(fmt_ctx, type, -1, -1, NULL, 0);
	if (ret < 0) {
	fprintf(stderr, "Could not find %s stream in input file '%s'\n",
	av_get_media_type_string(type), src_filename);
	return ret;
	} else {
	stream_index = ret;
	st = fmt_ctx->streams[stream_index];

	/* find decoder for the stream */
	dec = avcodec_find_decoder(st->codecpar->codec_id);
	if (!dec) {
	fprintf(stderr, "Failed to find %s codec\n",
	av_get_media_type_string(type));
	return AVERROR(EINVAL);
	}

	/* Allocate a codec context for the decoder */
	*dec_ctx = avcodec_alloc_context3(dec);
	if (!*dec_ctx) {
	fprintf(stderr, "Failed to allocate the %s codec context\n",
	av_get_media_type_string(type));
	return AVERROR(ENOMEM);
	}

	/* Copy codec parameters from input stream to output codec context */
	if ((ret = avcodec_parameters_to_context(*dec_ctx, st->codecpar)) < 0) {
	fprintf(stderr, "Failed to copy %s codec parameters to decoder context\n",
	av_get_media_type_string(type));
	return ret;
	}

	/* Init the decoders */
	if ((ret = avcodec_open2(*dec_ctx, dec, &opts)) < 0) {
	fprintf(stderr, "Failed to open %s codec\n",
	av_get_media_type_string(type));
	return ret;
	}
	*stream_idx = stream_index;
	}

	return 0;
	}

	static int get_format_from_sample_fmt(const char **fmt,
	enum AVSampleFormat sample_fmt)
	{
	int i;
	struct sample_fmt_entry {
	enum AVSampleFormat sample_fmt; const char fmt_be, fmt_le;
	} sample_fmt_entries[] = {
	{ AV_SAMPLE_FMT_U8, "u8", "u8" },
	{ AV_SAMPLE_FMT_S16, "s16be", "s16le" },
	{ AV_SAMPLE_FMT_S32, "s32be", "s32le" },
	{ AV_SAMPLE_FMT_FLT, "f32be", "f32le" },
	{ AV_SAMPLE_FMT_DBL, "f64be", "f64le" },
	};
	*fmt = NULL;

	for (i = 0; i < FF_ARRAY_ELEMS(sample_fmt_entries); i++) {
	struct sample_fmt_entry *entry = &sample_fmt_entries[i];
	if (sample_fmt == entry->sample_fmt) {
	*fmt = AV_NE(entry->fmt_be, entry->fmt_le);
	return 0;
	}
	}

	fprintf(stderr,
	"sample format %s is not supported as output format\n",
	av_get_sample_fmt_name(sample_fmt));
	return -1;
	}

	int main (int argc, char **argv)
	{
	int ret = 0;

	if (argc != 4) {
	fprintf(stderr, "usage: %s input_file video_output_file audio_output_file\n"
	"API example program to show how to read frames from an input file.\n"
	"This program reads frames from a file, decodes them, and writes decoded\n"
	"video frames to a rawvideo file named video_output_file, and decoded\n"
	"audio frames to a rawaudio file named audio_output_file.\n",
	argv[0]);
	exit(1);
	}
	src_filename = argv[1];
	video_dst_filename = argv[2];
	audio_dst_filename = argv[3];

	/* open input file, and allocate format context */
	if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0) {
	fprintf(stderr, "Could not open source file %s\n", src_filename);
	exit(1);
	}

	/* retrieve stream information */
	if (avformat_find_stream_info(fmt_ctx, NULL) < 0) {
	fprintf(stderr, "Could not find stream information\n");
	exit(1);
	}

	if (open_codec_context(&video_stream_idx, &video_dec_ctx, fmt_ctx, AVMEDIA_TYPE_VIDEO) >= 0) {
	video_stream = fmt_ctx->streams[video_stream_idx];

	video_dst_file = fopen(video_dst_filename, "wb");
	if (!video_dst_file) {
	fprintf(stderr, "Could not open destination file %s\n", video_dst_filename);
	ret = 1;
	goto end;
	}

	/* allocate image where the decoded image will be put */
	width = video_dec_ctx->width;
	height = video_dec_ctx->height;
	pix_fmt = video_dec_ctx->pix_fmt;
	ret = av_image_alloc(video_dst_data, video_dst_linesize,
	width, height, pix_fmt, 1);
	if (ret < 0) {
	fprintf(stderr, "Could not allocate raw video buffer\n");
	goto end;
	}
	video_dst_bufsize = ret;
	}

	if (open_codec_context(&audio_stream_idx, &audio_dec_ctx, fmt_ctx, AVMEDIA_TYPE_AUDIO) >= 0) {
	audio_stream = fmt_ctx->streams[audio_stream_idx];
	audio_dst_file = fopen(audio_dst_filename, "wb");
	if (!audio_dst_file) {
	fprintf(stderr, "Could not open destination file %s\n", audio_dst_filename);
	ret = 1;
	goto end;
	}
	}

	/* dump input information to stderr */
	av_dump_format(fmt_ctx, 0, src_filename, 0);

	if (!audio_stream && !video_stream) {
	fprintf(stderr, "Could not find audio or video stream in the input, aborting\n");
	ret = 1;
	goto end;
	}

	frame = av_frame_alloc();
	if (!frame) {
	fprintf(stderr, "Could not allocate frame\n");
	ret = AVERROR(ENOMEM);
	goto end;
	}

	/* initialize packet, set data to NULL, let the demuxer fill it */
	av_init_packet(&pkt);
	pkt.data = NULL;
	pkt.size = 0;

	if (video_stream)
	printf("Demuxing video from file '%s' into '%s'\n", src_filename, video_dst_filename);
	if (audio_stream)
	printf("Demuxing audio from file '%s' into '%s'\n", src_filename, audio_dst_filename);

	/* read frames from the file */
	while (av_read_frame(fmt_ctx, &pkt) >= 0) {
	// check if the packet belongs to a stream we are interested in, otherwise
	// skip it
	if (pkt.stream_index == video_stream_idx)
	ret = decode_packet(video_dec_ctx, &pkt);
	else if (pkt.stream_index == audio_stream_idx)
	ret = decode_packet(audio_dec_ctx, &pkt);
	av_packet_unref(&pkt);
	if (ret < 0)
	break;
	}

	/* flush the decoders */
	if (video_dec_ctx)
	decode_packet(video_dec_ctx, NULL);
	if (audio_dec_ctx)
	decode_packet(audio_dec_ctx, NULL);

	printf("Demuxing succeeded.\n");

	if (video_stream) {
	printf("Play the output video file with the command:\n"
	"ffplay -f rawvideo -pix_fmt %s -video_size %dx%d %s\n",
	av_get_pix_fmt_name(pix_fmt), width, height,
	video_dst_filename);
	}

	if (audio_stream) {
	enum AVSampleFormat sfmt = audio_dec_ctx->sample_fmt;
	int n_channels = audio_dec_ctx->channels;
	const char *fmt;

	if (av_sample_fmt_is_planar(sfmt)) {
	const char *packed = av_get_sample_fmt_name(sfmt);
	printf("Warning: the sample format the decoder produced is planar "
	"(%s). This example will output the first channel only.\n",
	packed ? packed : "?");
	sfmt = av_get_packed_sample_fmt(sfmt);
	n_channels = 1;
	}

	if ((ret = get_format_from_sample_fmt(&fmt, sfmt)) < 0)
	goto end;

	printf("Play the output audio file with the command:\n"
	"ffplay -f %s -ac %d -ar %d %s\n",
	fmt, n_channels, audio_dec_ctx->sample_rate,
	audio_dst_filename);
	}

	end:
	avcodec_free_context(&video_dec_ctx);
	avcodec_free_context(&audio_dec_ctx);
	avformat_close_input(&fmt_ctx);
	if (video_dst_file)
	fclose(video_dst_file);
	if (audio_dst_file)
	fclose(audio_dst_file);
	av_frame_free(&frame);
	av_free(video_dst_data[0]);

	return ret < 0;
	}