Pushing data to web-browser while processing input

Question

I want to push output of this directly to the user using PHP/Python:

wget -qO- "http://my-video-stream-input.url/here" | ffmpeg -i pipe:0 -ab 192000 -acodec libmp3lame -map_metadata -1 -vn 1378457645_myfile.mp3

The above command takes the input stream and converts on-the-fly it to audio without waiting for full-file to download, this works perfectly at terminal. Now, I need to push the ffmpeg processed output audio to the web-browser, once again on-the-fly without completing the full transcode, like :

Wget->ffmpeg->Web-browser in real-time

I tried the below in PHP but this results in 0 byte file-downloads:

$cmd = "wget -qO- "http://my-video-stream-input.url/here" | ffmpeg -i pipe:0 -ab 192000 -acodec libmp3lame -map_metadata -1 -vn 1378457645_myfile.mp3";
header('Content-type: audio/mpeg');
header("Content-Type: application/octet-stream");
header("Content-Disposition: attachment; filename=\"1378457645_myfile.mp3\"");
passthru($cmd);

Adding 2>&1 to the $cmd shows downloads a 3.6 KB file with following

  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%

Answer 1

You need to tell ffmpeg to output data to stdout, rather than giving it a file name. For example, the following command reads an input in FLAC format from stdin and writes an output in MP3 format to stdout (the file name "-" is used to mean stdin/stdout):

ffmpeg -f flac -i - -f mp3 -