36 #define INBUF_SIZE 4096 38 static void pgm_save(
unsigned char *buf,
int wrap,
int xsize,
int ysize,
44 f = fopen(filename,
"wb");
45 fprintf(f,
"P5\n%d %d\n%d\n", xsize, ysize, 255);
46 for (i = 0; i < ysize; i++)
47 fwrite(buf + i * wrap, 1, xsize, f);
59 fprintf(stderr,
"Error sending a packet for decoding\n");
68 fprintf(stderr,
"Error during decoding\n");
83 int main(
int argc,
char **argv)
85 const char *filename, *outfilename;
98 fprintf(stderr,
"Usage: %s <input file> <output file>\n" 99 "And check your input file is encoded by mpeg1video please.\n", argv[0]);
103 outfilename = argv[2];
115 fprintf(stderr,
"Codec not found\n");
121 fprintf(stderr,
"parser not found\n");
127 fprintf(stderr,
"Could not allocate video codec context\n");
137 fprintf(stderr,
"Could not open codec\n");
141 f = fopen(filename,
"rb");
143 fprintf(stderr,
"Could not open %s\n", filename);
149 fprintf(stderr,
"Could not allocate video frame\n");
161 while (data_size > 0) {
165 fprintf(stderr,
"Error while parsing\n");
172 decode(c, frame, pkt, outfilename);
This structure describes decoded (raw) audio or video data.
ptrdiff_t const GLvoid * data
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, char *filename)
int main(int argc, char **argv)
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
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
#define AVERROR_EOF
End of file.
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder.
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt, const char *filename)
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
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.
void av_parser_close(AVCodecParserContext *s)
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several the filter must be ready for frames arriving randomly on any input any filter with several inputs will most likely require some kind of queuing mechanism It is perfectly acceptable to have a limited queue and to drop frames when the inputs are too unbalanced request_frame For filters that do not use the this method is called when a frame is wanted on an output For a it should directly call filter_frame on the corresponding output For a if there are queued frames already one of these frames should be pushed If the filter should request a frame on one of its repeatedly until at least one frame has been pushed Return or at least make progress towards producing a frame
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
AVCodecParserContext * av_parser_init(int codec_id)
Libavcodec external API header.
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer...
int linesize[AV_NUM_DATA_POINTERS]
For video, size in bytes of each picture line.
main external API structure.
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
AVCodec * avcodec_find_decoder(enum AVCodecID id)
Find a registered decoder with a matching codec ID.
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
static AVCodecContext * dec_ctx
#define AV_INPUT_BUFFER_PADDING_SIZE
Required number of additionally allocated bytes at the end of the input bitstream for decoding...
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 frame_number
Frame counter, set by libavcodec.
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
This structure stores compressed data.
#define AV_NOPTS_VALUE
Undefined timestamp value.