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examples/decode_video: use a parser for splitting the input

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Do not rely on the decoder handling this, as it's not guaranteed to
work.
This commit is contained in:
Anton Khirnov 2016-10-19 21:56:22 +02:00
parent 59ab9e8ba1
commit f78d360bba
1 changed files with 55 additions and 56 deletions
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111
doc/examples/decode_video.c
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@ -50,16 +50,45 @@ static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
fclose(f);
}
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
const char *filename)
{
char buf[1024];
int ret, got_picture;
while (pkt->size > 0) {
ret = avcodec_decode_video2(dec_ctx, frame, &got_picture, pkt);
if (ret < 0) {
fprintf(stderr, "Error while decoding frame %d\n", dec_ctx->frame_number);
exit(1);
}
if (got_picture) {
printf("saving frame %3d\n", dec_ctx->frame_number);
fflush(stdout);
/* the picture is allocated by the decoder. no need to
free it */
snprintf(buf, sizeof(buf), filename, dec_ctx->frame_number);
pgm_save(frame->data[0], frame->linesize[0],
frame->width, frame->height, buf);
}
pkt->size -= ret;
pkt->data += ret;
}
}
int main(int argc, char **argv)
{
const char *filename, *outfilename;
const AVCodec *codec;
AVCodecParserContext *parser;
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];
uint8_t *data;
size_t data_size;
int ret;
AVPacket avpkt;
if (argc <= 2) {
@ -83,12 +112,15 @@ int main(int argc, char **argv)
exit(1);
}
parser = av_parser_init(codec->id);
if (!parser) {
fprintf(stderr, "parser 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. */
@ -105,70 +137,37 @@ int main(int argc, char **argv)
exit(1);
}
frame = 0;
for(;;) {
avpkt.size = fread(inbuf, 1, INBUF_SIZE, f);
if (avpkt.size == 0)
while (!feof(f)) {
/* read raw data from the input file */
data_size = fread(inbuf, 1, INBUF_SIZE, f);
if (!data_size)
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);
/* use the parser to split the data into frames */
data = inbuf;
while (data_size > 0) {
ret = av_parser_parse2(parser, c, &avpkt.data, &avpkt.size,
data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
if (ret < 0) {
fprintf(stderr, "Error while parsing\n");
exit(1);
}
if (got_picture) {
printf("saving frame %3d\n", frame);
fflush(stdout);
data += ret;
data_size -= ret;
/* 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;
if (avpkt.size)
decode(c, picture, &avpkt, outfilename);
}
}
/* 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. */
/* flush the decoder */
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++;
}
decode(c, picture, &avpkt, outfilename);
fclose(f);
av_parser_close(parser);
avcodec_free_context(&c);
av_frame_free(&picture);