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examples/demuxing_decoding: abort decoding when width, height or pix_fmt change 

This is necessary, because avcodec_decode_video2 can change
width, height and/or pixel format of the AVCodecContext. Since
video_dst_data and video_dst_linesize are not updated by calling
av_image_alloc again, av_image_copy[_plane] asserts, because the
destination buffer is too small.

In this case, creating a useable rawvideo is not possible anyway, since
it has fixed width/height/pix_fmt.

Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Andreas Cadhalpun 2015-01-31 20:36:07 +01:00 committed by Michael Niedermayer
parent 06fe6dfe12
commit 078be09dd7
1 changed files with 22 additions and 4 deletions
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26
doc/examples/demuxing_decoding.c
View File

@ -36,6 +36,8 @@
static AVFormatContext *fmt_ctx = NULL; static AVFormatContext *fmt_ctx = NULL;
static AVCodecContext *video_dec_ctx = NULL, *audio_dec_ctx; 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 AVStream *video_stream = NULL, *audio_stream = NULL;
static const char *src_filename = NULL; static const char *src_filename = NULL;
static const char *video_dst_filename = NULL; static const char *video_dst_filename = NULL;
@ -79,6 +81,20 @@ static int decode_packet(int *got_frame, int cached)
fprintf(stderr, "Error decoding video frame (%s)\n", av_err2str(ret)); fprintf(stderr, "Error decoding video frame (%s)\n", av_err2str(ret));
return ret; return ret;
} }
if (video_dec_ctx->width != width || video_dec_ctx->height != height ||
video_dec_ctx->pix_fmt != 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),
video_dec_ctx->width, video_dec_ctx->height,
av_get_pix_fmt_name(video_dec_ctx->pix_fmt));
return -1;
}
if (*got_frame) { if (*got_frame) {
printf("video_frame%s n:%d coded_n:%d pts:%s\n", printf("video_frame%s n:%d coded_n:%d pts:%s\n",
@ -90,7 +106,7 @@ static int decode_packet(int *got_frame, int cached)
* this is required since rawvideo expects non aligned data */ * this is required since rawvideo expects non aligned data */
av_image_copy(video_dst_data, video_dst_linesize, av_image_copy(video_dst_data, video_dst_linesize,
(const uint8_t **)(frame->data), frame->linesize, (const uint8_t **)(frame->data), frame->linesize,
video_dec_ctx->pix_fmt, video_dec_ctx->width, video_dec_ctx->height); pix_fmt, width, height);
/* write to rawvideo file */ /* write to rawvideo file */
fwrite(video_dst_data[0], 1, video_dst_bufsize, video_dst_file); fwrite(video_dst_data[0], 1, video_dst_bufsize, video_dst_file);
@ -265,9 +281,11 @@ int main (int argc, char **argv)
} }
/* allocate image where the decoded image will be put */ /* 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, ret = av_image_alloc(video_dst_data, video_dst_linesize,
video_dec_ctx->width, video_dec_ctx->height, width, height, pix_fmt, 1);
video_dec_ctx->pix_fmt, 1);
if (ret < 0) { if (ret < 0) {
fprintf(stderr, "Could not allocate raw video buffer\n"); fprintf(stderr, "Could not allocate raw video buffer\n");
goto end; goto end;
@ -342,7 +360,7 @@ int main (int argc, char **argv)
if (video_stream) { if (video_stream) {
printf("Play the output video file with the command:\n" printf("Play the output video file with the command:\n"
"ffplay -f rawvideo -pix_fmt %s -video_size %dx%d %s\n", "ffplay -f rawvideo -pix_fmt %s -video_size %dx%d %s\n",
av_get_pix_fmt_name(video_dec_ctx->pix_fmt), video_dec_ctx->width, video_dec_ctx->height, av_get_pix_fmt_name(pix_fmt), width, height,
video_dst_filename); video_dst_filename);
} }