我编写了一个模拟相机并将输出转换为视频流的程序。该程序必须能够在Windows上运行。 系统中有两个组件：
copy命令每0.1秒将预先生成的帧（即PNG文件）复制到目标路径./target/target_image.png ffmpeg -loop 1 -i ./target/target_image.png -r 10 -vcodec mpeg4 -f mpegts udp://127.0.0.1:1234 当一起运行整个过程时，它会正常工作几秒钟，直到ffmpeg停止。这是在调试模式下运行时的日志：
ffmpeg version N-52458-gaa96439 Copyright (c) 2000-2013 the FFmpeg developers
built on Apr 24 2013 22:19:32 with gcc 4.8.0 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetype --enable-libgsm --enable-libilbc --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
libavutil 52. 27.101 / 52. 27.101
libavcodec 55. 6.100 / 55. 6.100
libavformat 55. 3.100 / 55. 3.100
libavdevice 55. 0.100 / 55. 0.100
libavfilter 3. 60.101 / 3. 60.101
libswscale 2. 2.100 / 2. 2.100
libswresample 0. 17.102 / 0. 17.102
libpostproc 52. 3.100 / 52. 3.100
Splitting the commandline.
Reading option '-loop' ... matched as AVOption 'loop' with argument '1'.
Reading option '-i' ... matched as input file with argument './target/target_image.png'.
Reading option '-r' ... matched as option 'r' (set frame rate (Hz value, fraction or abbreviation)) with argument '10'.
Reading option '-vcodec' ... matched as option 'vcodec' (force video codec ('copy' to copy stream)) with argument 'mpeg4'.
Reading option '-f' ... matched as option 'f' (force format) with argument 'mpegts'.
Reading option 'udp://127.0.0.1:1234' ... matched as output file.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option loglevel (set logging level) with argument debug.
Successfully parsed a group of options.
Parsing a group of options: input file ./target/target_image.png.
Successfully parsed a group of options.
Opening an input file: ./target/target_image.png.
[AVIOContext @ 02678840] Statistics: 234307 bytes read, 0 seeks
[AVIOContext @ 02678840] Statistics: 221345 bytes read, 0 seeks
Last message repeated 1 times
[AVIOContext @ 02678840] Statistics: 226329 bytes read, 0 seeks
Last message repeated 2 times
[AVIOContext @ 02678840] Statistics: 228676 bytes read, 0 seeks
Last message repeated 2 times
[AVIOContext @ 02678840] Statistics: 230685 bytes read, 0 seeks
Last message repeated 2 times
[AVIOContext @ 02678840] Statistics: 232697 bytes read, 0 seeks
Last message repeated 5 times
[AVIOContext @ 02678840] Statistics: 234900 bytes read, 0 seeks
Last message repeated 2 times
[AVIOContext @ 02678840] Statistics: 236847 bytes read, 0 seeks
[image2 @ 02677ac0] Probe buffer size limit of 5000000 bytes reached
Input #0, image2, from './target/target_image.png':
Duration: 00:00:00.04, start: 0.000000, bitrate: N/A
Stream #0:0, 22, 1/25: Video: png, rgb24, 1274x772 [SAR 1:1 DAR 637:386], 1/25, 25 fps, 25 tbr, 25 tbn, 25 tbc
Successfully opened the file.
Parsing a group of options: output file udp://127.0.0.1:1234.
Applying option r (set frame rate (Hz value, fraction or abbreviation)) with argument 10.
Applying option vcodec (force video codec ('copy' to copy stream)) with argument mpeg4.
Applying option f (force format) with argument mpegts.
Successfully parsed a group of options.
Opening an output file: udp://127.0.0.1:1234.
Successfully opened the file.
[graph 0 input from stream 0:0 @ 02769280] Setting 'video_size' to value '1274x772'
[graph 0 input from stream 0:0 @ 02769280] Setting 'pix_fmt' to value '2'
[graph 0 input from stream 0:0 @ 02769280] Setting 'time_base' to value '1/25'
[graph 0 input from stream 0:0 @ 02769280] Setting 'pixel_aspect' to value '1/1'
[graph 0 input from stream 0:0 @ 02769280] Setting 'sws_param' to value 'flags=2'
[graph 0 input from stream 0:0 @ 02769280] Setting 'frame_rate' to value '25/1'
[graph 0 input from stream 0:0 @ 02769280] w:1274 h:772 pixfmt:rgb24 tb:1/25 fr:25/1 sar:1/1 sws_param:flags=2
[format @ 02768ba0] compat: called with args=[yuv420p]
[format @ 02768ba0] Setting 'pix_fmts' to value 'yuv420p'
[auto-inserted scaler 0 @ 02768740] Setting 'w' to value '0'
[auto-inserted scaler 0 @ 02768740] Setting 'h' to value '0'
[auto-inserted scaler 0 @ 02768740] Setting 'flags' to value '0x4'
[auto-inserted scaler 0 @ 02768740] w:0 h:0 flags:'0x4' interl:0
[format @ 02768ba0] auto-inserting filter 'auto-inserted scaler 0' between the filter 'Parsed_null_0' and the filter 'format'
[AVFilterGraph @ 026772c0] query_formats: 4 queried, 3 merged, 1 already done, 0 delayed
[auto-inserted scaler 0 @ 02768740] w:1274 h:772 fmt:rgb24 sar:1/1 -> w:1274 h:772 fmt:yuv420p sar:1/1 flags:0x4
[mpeg4 @ 02785020] detected 4 logical cores
[mpeg4 @ 02785020] intra_quant_bias = 0 inter_quant_bias = -64
[mpegts @ 0277da40] muxrate VBR, pcr every 1 pkts, sdt every 200, pat/pmt every 40 pkts
Output #0, mpegts, to 'udp://127.0.0.1:1234':
Metadata:
encoder : Lavf55.3.100
Stream #0:0, 0, 1/90000: Video: mpeg4, yuv420p, 1274x772 [SAR 1:1 DAR 637:386], 1/10, q=2-31, 200 kb/s, 90k tbn, 10 tbc
Stream mapping:
Stream #0:0 -> #0:0 (png -> mpeg4)
Press [q] to stop, [?] for help
*** drop!
Last message repeated 10 times
frame= 11 fps=0.0 q=4.0 size= 118kB time=00:00:01.10 bitrate= 875.1kbits/s dup=0 drop=11
Statistics: 242771 bytes read, 0 seeks
[AVIOContext @ 02674a60] Statistics: 246525 bytes read, 0 seeks
*** drop!
[AVIOContext @ 02674a60] Statistics: 230678 bytes read, 0 seeks
[AVIOContext @ 02674a60] Statistics: 244023 bytes read, 0 seeks
*** drop!
[AVIOContext @ 02674a60] Statistics: 246389 bytes read, 0 seeks
*** drop!
[AVIOContext @ 02674a60] Statistics: 224478 bytes read, 0 seeks
[AVIOContext @ 02674a60] Statistics: 228013 bytes read, 0 seeks
*** drop!
[image2 @ 02677ac0] Could not open file : ./target/target_image.png
./target/target_image.png: Input/output error
[output stream 0:0 @ 02768c20] EOF on sink link output stream 0:0:default.
No more output streams to write to, finishing.
frame= 164 fps= 17 q=31.0 Lsize= 959kB time=00:00:16.40 bitrate= 478.9kbits/s dup=0 drop=240
video:869kB audio:0kB subtitle:0 global headers:0kB muxing overhead 10.285235%
404 frames successfully decoded, 0 decoding errors
[AVIOContext @ 026779c0] Statistics: 0 seeks, 746 writeouts
在我看来，读/写同一文件之间存在某种冲突。有趣的是，在Linux上（将copy替换为cp时），该程序运行正常。
有人可以提出解决此问题的方法吗？只要逻辑工作流程保持不变，替代解决方案也是可接受的。
答案 0 :(得分：4)
在Nick van Tilborg的评论之后，我最终使用了FFmpeg的image2pipe。此功能允许将图像数据简化为FFmpeg，而不是同时访问同一文件的两个进程。
下面是我写的C ++代码。它可能没有完全优化，但它完成了工作。它是在Windows 7上使用Visual Studio 2012编译和测试的。
#include "stdafx.h"
#include "windows.h"
#include "iostream"
#include "stdio.h"
using namespace std;
#pragma warning (disable : 4996)
int _tmain(int argc, _TCHAR* argv[])
{
int count;
int times = 2200;
FILE *pPipe;
FILE * pFile;
long lSize;
char * buffer;
size_t result;
// open a pipe to FFmpeg
if( (pPipe = _popen( "ffmpeg -re -f image2pipe -vcodec mjpeg -i - -vcodec h264 -r 10 -f mpegts udp://127.0.0.1:1234", "wb")) == NULL ) {exit( 1 );}
for ( count = 1; count <= times; count++) {
char filename[40];
sprintf(&filename[0], ".\\images\\image-%07d.jpg", count);
pFile = fopen ( filename , "rb" );
if (pFile==NULL) {fputs ("File error",stderr); exit (2);}
// obtain file size:
fseek (pFile , 0 , SEEK_END);
lSize = ftell (pFile);
rewind (pFile);
// allocate memory to contain the whole file:
buffer = (char*) malloc (sizeof(char)*lSize);
if (buffer == NULL) {fputs ("Memory error",stderr); exit (3);}
// copy the file into the buffer:
result = fread (buffer, 1, lSize, pFile);
if (result != lSize) {fputs ("Reading error",stderr); exit (4);}
// write to pipe
fwrite(buffer, 1, lSize, pPipe);
fflush(pPipe);
// clean
fclose (pFile);
free (buffer);
//
Sleep(100);
}
//
return 0;
}
答案 1 :(得分：2)
使用当前命令行，FFmpeg以尽可能高的速度运行。这意味着FFmpeg不是以10 fps的速度读取帧，而是尽可能快地读取帧。它也不以10 fps传输传输流。因为您的程序是以10 fps的速度固定写入帧，所以这有时候您可能无法读取文件，因为文件是在这些特定时间写入的。
要解决此问题，请尝试使用FFmpeg命令行中的-re标志强制FFmpeg以本机帧速率读取输入。
ffmpeg -re -loop 1 -i ./target/target_image.png -r 10 -vcodec mpeg4 -f mpegts udp://127.0.0.1:1234