#11546: mjpeg file call av_read_frame return EOF after seek
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Reporter: honglongyu | Type: defect
Status: new | Priority: normal
Component: avcodec | Version: git-master
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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I'm working on a looped decoding scenario for MJPEG files, and I
encountered an issue when seeking back to the beginning of the file.
Specifically, after calling av_seek_frame(fmt_ctx, -1, 0,
AVSEEK_FLAG_BACKWARD), the first packet returned by av_read_frame() is
immediately an EOF.
Below is a minimal demo of my decoding code:
{{{
#include <iostream>
extern "C" {
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
}
int main() {
const char* filename =
"D:\\dev\\8k_main\\8k\\example\\decode_pic\\test.jpg";
AVFormatContext* formatContext = nullptr;
if (avformat_open_input(&formatContext, filename, nullptr, nullptr) !=
0) {
std::cerr << "Could not open file: " << filename << std::endl;
return -1;
}
if (avformat_find_stream_info(formatContext, nullptr) < 0) {
std::cerr << "FFmpeg failed to find stream info: " << filename
<< std::endl;
return -1;
}
av_dump_format(formatContext, 0, filename, 0);
int ret_seek = av_seek_frame(formatContext, 0, 0,
AVSEEK_FLAG_BACKWARD);
if (ret_seek < 0) {
std::cerr << "Error seeking to frame" << std::endl;
avformat_close_input(&formatContext);
return -1;
}
// Read a frame from the file
AVPacket packet;
int ret = av_read_frame(formatContext, &packet);
if (ret < 0) {
char errbuf[AV_ERROR_MAX_STRING_SIZE] = {0};
av_strerror(ret, errbuf, sizeof(errbuf));
std::cerr << "Error reading frame, err is " << errbuf <<
std::endl;
av_packet_unref(&packet);
avformat_close_input(&formatContext);
return -1;
}
std::cout << "Frame read successfully" << std::endl;
return 0;
}
}}}
Here is the console output with seek:
{{{
Input #0, image2, from 'D:\dev\8k_main\8k\example\decode_pic\test.jpg':
Duration: 00:00:00.04, start: 0.000000, bitrate: 551200 kb/s
Stream #0:0: Video: mjpeg (Baseline), yuvj420p(pc,
bt470bg/unknown/unknown), 3840x2160 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 25
tbn
Error reading frame, err is End of file
}}}
And here is the output without calling seek:
{{{
Input #0, image2, from 'D:\dev\8k_main\8k\example\decode_pic\test.jpg':
Duration: 00:00:00.04, start: 0.000000, bitrate: 551200 kb/s
Stream #0:0: Video: mjpeg (Baseline), yuvj420p(pc,
bt470bg/unknown/unknown), 3840x2160 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 25
tbn
Frame read successfully
}}}
--
Ticket URL: <https://trac.ffmpeg.org/ticket/11546>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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