*Read from an MPEG1 video file, decode frames, and generate PGM images as output.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define INBUF_SIZE 4096
static void pgm_save(
unsigned char *buf,
int wrap,
int xsize,
int ysize,
char *filename)
{
f = fopen(filename,
"wb");
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);
}
const char *filename)
{
char buf[1024];
fprintf(stderr, "Error sending a packet for decoding\n");
exit(1);
}
return;
fprintf(stderr, "Error during decoding\n");
exit(1);
}
fflush(stdout);
}
}
int main(
int argc,
char **argv)
{
const char *filename, *outfilename;
size_t data_size;
int eof;
if (argc <= 2) {
fprintf(stderr, "Usage: %s <input file> <output file>\n"
"And check your input file is encoded by mpeg1video please.\n", argv[0]);
exit(0);
}
filename = argv[1];
outfilename = argv[2];
exit(1);
if (!codec) {
fprintf(stderr, "Codec not found\n");
exit(1);
}
if (!parser) {
fprintf(stderr, "parser not found\n");
exit(1);
}
fprintf(stderr, "Could not allocate video codec context\n");
exit(1);
}
fprintf(stderr, "Could not open codec\n");
exit(1);
}
f = fopen(filename,
"rb");
fprintf(stderr, "Could not open %s\n", filename);
exit(1);
}
fprintf(stderr, "Could not allocate video frame\n");
exit(1);
}
do {
break;
eof = !data_size;
while (data_size > 0 || eof) {
fprintf(stderr, "Error while parsing\n");
exit(1);
}
else if (eof)
break;
}
} while (!eof);
return 0;
}
static AVCodecContext * dec_ctx
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
#define AVERROR_EOF
End of file.
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
This structure describes decoded (raw) audio or video data.
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, char *filename)
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
AVCodecParserContext * av_parser_init(int codec_id)
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
int attribute_align_arg avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder or encoder (when the AV_CODEC_FLAG_RECON_FRAME flag is used...
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt, const char *filename)
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer.
int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
const AVCodec * avcodec_find_decoder(enum AVCodecID id)
Find a registered decoder with a matching codec ID.
#define AV_NOPTS_VALUE
Undefined timestamp value.
printf("static const uint8_t my_array[100] = {\n")
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
#define i(width, name, range_min, range_max)
int64_t frame_num
Frame counter, set by libavcodec.
#define AV_INPUT_BUFFER_PADDING_SIZE
main external API structure.
int av_parser_parse2(AVCodecParserContext *s, AVCodecContext *avctx, uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size, int64_t pts, int64_t dts, int64_t pos)
Parse a packet.
This structure stores compressed data.
int linesize[AV_NUM_DATA_POINTERS]
For video, a positive or negative value, which is typically indicating the size in bytes of each pict...
int main(int argc, char **argv)
void av_parser_close(AVCodecParserContext *s)