diff options
author | Anton Khirnov <anton@khirnov.net> | 2016-10-19 21:05:22 +0200 |
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committer | Anton Khirnov <anton@khirnov.net> | 2016-11-02 10:16:04 +0100 |
commit | 7b1f03477f1a43d2261fbd83e50a4ad90c7f806d (patch) | |
tree | cc6c48d43c5abd69b99baeeb9cde003a76a0180f /doc/examples/decode_video.c | |
parent | 90265814f993098d79b0a0f40745ecdb403fbf56 (diff) |
examples/avcodec: split the remaining two examples into separate files
Diffstat (limited to 'doc/examples/decode_video.c')
-rw-r--r-- | doc/examples/decode_video.c | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/doc/examples/decode_video.c b/doc/examples/decode_video.c new file mode 100644 index 0000000000..20d11dae4e --- /dev/null +++ b/doc/examples/decode_video.c @@ -0,0 +1,178 @@ +/* + * copyright (c) 2001 Fabrice Bellard + * + * This file is part of Libav. + * + * Libav is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * Libav is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with Libav; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +/** + * @file + * video decoding with libavcodec API example + * + * @example decode_video.c + */ + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#include "libavcodec/avcodec.h" + +#include "libavutil/common.h" +#include "libavutil/imgutils.h" +#include "libavutil/mathematics.h" + +#define INBUF_SIZE 4096 + +static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, + char *filename) +{ + FILE *f; + int i; + + f=fopen(filename,"w"); + fprintf(f,"P5\n%d %d\n%d\n",xsize,ysize,255); + for(i=0;i<ysize;i++) + fwrite(buf + i * wrap,1,xsize,f); + fclose(f); +} + +int main(int argc, char **argv) +{ + const char *filename, *outfilename; + AVCodec *codec; + AVCodecContext *c= NULL; + int frame, got_picture, len; + FILE *f; + AVFrame *picture; + uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE]; + char buf[1024]; + AVPacket avpkt; + + if (argc <= 2) { + fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]); + exit(0); + } + filename = argv[1]; + outfilename = argv[2]; + + avcodec_register_all(); + + av_init_packet(&avpkt); + + /* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */ + memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE); + + /* find the MPEG-1 video decoder */ + codec = avcodec_find_decoder(AV_CODEC_ID_MPEG1VIDEO); + if (!codec) { + fprintf(stderr, "codec not found\n"); + exit(1); + } + + c = avcodec_alloc_context3(codec); + picture = av_frame_alloc(); + + if (codec->capabilities & AV_CODEC_CAP_TRUNCATED) + c->flags |= AV_CODEC_FLAG_TRUNCATED; // we do not send complete frames + + /* For some codecs, such as msmpeg4 and mpeg4, width and height + MUST be initialized there because this information is not + available in the bitstream. */ + + /* open it */ + if (avcodec_open2(c, codec, NULL) < 0) { + fprintf(stderr, "could not open codec\n"); + exit(1); + } + + /* the codec gives us the frame size, in samples */ + + f = fopen(filename, "rb"); + if (!f) { + fprintf(stderr, "could not open %s\n", filename); + exit(1); + } + + frame = 0; + for(;;) { + avpkt.size = fread(inbuf, 1, INBUF_SIZE, f); + if (avpkt.size == 0) + break; + + /* NOTE1: some codecs are stream based (mpegvideo, mpegaudio) + and this is the only method to use them because you cannot + know the compressed data size before analysing it. + + BUT some other codecs (msmpeg4, mpeg4) are inherently frame + based, so you must call them with all the data for one + frame exactly. You must also initialize 'width' and + 'height' before initializing them. */ + + /* NOTE2: some codecs allow the raw parameters (frame size, + sample rate) to be changed at any frame. We handle this, so + you should also take care of it */ + + /* here, we use a stream based decoder (mpeg1video), so we + feed decoder and see if it could decode a frame */ + avpkt.data = inbuf; + while (avpkt.size > 0) { + len = avcodec_decode_video2(c, picture, &got_picture, &avpkt); + if (len < 0) { + fprintf(stderr, "Error while decoding frame %d\n", frame); + exit(1); + } + if (got_picture) { + printf("saving frame %3d\n", frame); + fflush(stdout); + + /* the picture is allocated by the decoder. no need to + free it */ + snprintf(buf, sizeof(buf), outfilename, frame); + pgm_save(picture->data[0], picture->linesize[0], + c->width, c->height, buf); + frame++; + } + avpkt.size -= len; + avpkt.data += len; + } + } + + /* Some codecs, such as MPEG, transmit the I- and P-frame with a + latency of one frame. You must do the following to have a + chance to get the last frame of the video. */ + avpkt.data = NULL; + avpkt.size = 0; + len = avcodec_decode_video2(c, picture, &got_picture, &avpkt); + if (got_picture) { + printf("saving last frame %3d\n", frame); + fflush(stdout); + + /* the picture is allocated by the decoder. no need to + free it */ + snprintf(buf, sizeof(buf), outfilename, frame); + pgm_save(picture->data[0], picture->linesize[0], + c->width, c->height, buf); + frame++; + } + + fclose(f); + + avcodec_free_context(&c); + av_frame_free(&picture); + + return 0; +} |