我想使用 PHP/Python 将它的输出直接推送给用户：
wget -qO- "http://my-video-stream-input.url/here" | ffmpeg -i pipe:0 -ab 192000 -acodec libmp3lame -map_metadata -1 -vn 1378457645_myfile.mp3
上面的命令获取输入流并将其即时转换为音频，而无需等待完整文件下载，这在终端上完美运行。现在，我需要将 ffmpeg 处理后的输出音频推送到网络浏览器，再次即时而不完成完整的转码，例如：
Wget->ffmpeg->实时网络浏览器
我在 PHP 中尝试了以下内容，但这会导致 0 字节文件下载：
$cmd = "wget -qO- "http://my-video-stream-input.url/here" | ffmpeg -i pipe:0 -ab 192000 -acodec libmp3lame -map_metadata -1 -vn 1378457645_myfile.mp3";
header('Content-type: audio/mpeg');
header("Content-Type: application/octet-stream");
header("Content-Disposition: attachment; filename=\"1378457645_myfile.mp3\"");
passthru($cmd);
添加 2>&1到 $cmd 显示下载一个 3.6 KB 的文件，其中包含以下内容
ffmpeg version 0.7.15, Copyright (c) 2000-2013 the FFmpeg developers
built on Feb 22 2013 07:22:31 with gcc 4.4.5
configuration: --enable-libdc1394 --prefix=/usr --extra-cflags='-Wall -g ' --cc='ccache cc' --enable-shared --enable-libmp3lame --enable-gpl --enable-libvorbis --enable-pthreads --enable-libfaac --enable-libxvid --enable-postproc --enable-x11grab --enable-libgsm --enable-libtheora --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264 --enable-libspeex --enable-nonfree --disable-stripping --enable-avfilter --enable-libdirac --disable-decoder=libdirac --enable-libfreetype --enable-libschroedinger --disable-encoder=libschroedinger --enable-version3 --enable-libopenjpeg --enable-libvpx --enable-librtmp --extra-libs=-lgcrypt --disable-altivec --disable-armv5te --disable-armv6 --disable-vis
libavutil 50. 43. 0 / 50. 43. 0
libavcodec 52.123. 0 / 52.123. 0
libavformat 52.111. 0 / 52.111. 0
libavdevice 52. 5. 0 / 52. 5. 0
libavfilter 1. 80. 0 / 1. 80. 0
libswscale 0. 14. 1 / 0. 14. 1
libpostproc 51. 2. 0 / 51. 2. 0
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'pipe:0':
Duration: 00:02:54.75, start: 164.745578, bitrate: N/A
Stream #0.0(und): Audio: aac, 44100 Hz, stereo, s16
Metadata:
creation_time : 2013-08-30 05:36:13
Output #0, mp3, to '1378458744_myfile.mp3':
Metadata:
TSSE : Lavf52.111.0
Stream #0.0(und): Audio: libmp3lame, 44100 Hz, stereo, s16, 192 kb/s
Metadata:
creation_time : 2013-08-30 05:36:13
Stream mapping:
Stream #0.0 -> #0.0
size= 134kB time=00:00:05.69 bitrate= 192.3kbits/s
size= 263kB time=00:00:11.23 bitrate= 192.1kbits/s
size= 386kB time=00:00:16.45 bitrate= 192.1kbits/s
size= 515kB time=00:00:21.96 bitrate= 192.1kbits/s
size= 637kB time=00:00:27.16 bitrate= 192.1kbits/s
size= 765kB time=00:00:32.62 bitrate= 192.0kbits/s
size= 884kB time=00:00:37.69 bitrate= 192.0kbits/s
size= 1011kB time=00:00:43.12 bitrate= 192.0kbits/s
size= 1134kB time=00:00:48.37 bitrate= 192.0kbits/s
size= 1253kB time=00:00:53.47 bitrate= 192.0kbits/s
size= 1379kB time=00:00:58.82 bitrate= 192.0kbits/s
size= 1508kB time=00:01:04.31 bitrate= 192.0kbits/s
size= 1632kB time=00:01:09.64 bitrate= 192.0kbits/s
size= 1758kB time=00:01:14.99 bitrate= 192.0kbits/s
size= 1883kB time=00:01:20.35 bitrate= 192.0kbits/s
size= 2010kB time=00:01:25.76 bitrate= 192.0kbits/s
size= 2141kB time=00:01:31.35 bitrate= 192.0kbits/s
size= 2265kB time=00:01:36.65 bitrate= 192.0kbits/s
size= 2389kB time=00:01:41.92 bitrate= 192.0kbits/s
size= 2515kB time=00:01:47.31 bitrate= 192.0kbits/s
size= 2637kB time=00:01:52.50 bitrate= 192.0kbits/s
size= 2767kB time=00:01:58.04 bitrate= 192.0kbits/s
size= 2888kB time=00:02:03.21 bitrate= 192.0kbits/s
size= 3017kB time=00:02:08.70 bitrate= 192.0kbits/s
size= 3142kB time=00:02:14.06 bitrate= 192.0kbits/s
size= 3266kB time=00:02:19.33 bitrate= 192.0kbits/s
size= 3391kB time=00:02:24.66 bitrate= 192.0kbits/s
size= 3518kB time=00:02:30.07 bitrate= 192.0kbits/s
size= 3650kB time=00:02:35.71 bitrate= 192.0kbits/s
size= 3778kB time=00:02:41.20 bitrate= 192.0kbits/s
size= 3862kB time=00:02:44.78 bitrate= 192.0kbits/s
video:0kB audio:3862kB global headers:0kB muxing overhead 0.004804%