avconv can't convert stream to MP4 file, fails with "Unable to set encoding parameters"

Question

I'm trying to script some testing of Wowza Media Server. Basically, I'm attempting to just beat the living bejeepers out of the thing. I have 5 slightly older computers, originally XP boxes, which I have installed Mint 15 on. I have a script that basically calls the file (or a symbolic link to the file) and takes it into avconv, then dumps it into null.

The idea here is that with 5 of these computers all starting a new thread every second, up to the max they can handle without freezing, we'll get a decent idea of what our current implementation can handle. The script I have works great, but only on some machines. The systems are all the same hardware, and I installed the same software on them in the beginning, although some of them may have had additional packages installed for various tasks since then. The command I issue in script is:

avconv version 0.8.6-6:0.8.6-1ubuntu2, Copyright (c) 2000-2013 the Libav developers
built on Mar 30 2013 22:20:06 with gcc 4.7.2
[h264 @ 0xd87ae0] mmco: unref short failure
[applehttp @ 0xd80d40] max_analyze_duration reached
[applehttp @ 0xd80d40] Estimating duration from bitrate, this may be inaccurate
Input #0, applehttp, from     'http://OUR_DOMAIN.com:1935/vod/_definst_/encode/video_file/00/00/00/12/13/mp4:TestFile.mp4/playlist.m3u8':
  Duration: 02:05:54.00, start: 27.728000, bitrate: N/A
    Stream #0.0: Data: [21][0][0][0] / 0x0015
    Metadata:
      variant_bitrate : 1610015
    Stream #0.1: Video: h264 (Main), yuv420p, 1280x720 [PAR 1:1 DAR 16:9], 23.98 tbr, 90k tbn, 47.95 tbc
    Metadata:
      variant_bitrate : 1610015
    Stream #0.2: Audio: aac, 48000 Hz, 5.1, s16
    Metadata:
      variant_bitrate : 1610015
[buffer @ 0x13e02c0] w:1280 h:720 pixfmt:yuv420p
[libvo_aacenc @ 0x12c49c0] Unable to set encoding parameters
Output #0, mp4, to '/dev/null':
    Stream #0.0: Video: mpeg4, yuv420p, 1280x720 [PAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 90k tbn, 23.98 tbc
    Metadata:
      variant_bitrate : 1610015
    Stream #0.1: Audio: libvo_aacenc, 48000 Hz, 5.1, s16, 200 kb/s
    Metadata:
      variant_bitrate : 1610015
Stream mapping:
  Stream #0:1 -> #0:0 (h264 -> mpeg4)
  Stream #0:2 -> #0:1 (aac -> libvo_aacenc)
Error while opening encoder for output stream #0:1 - maybe incorrect parameters such as bit_rate, rate, width or height

Any clues would be greatly appreciated. Thanks!

Answer 1

The problem seems to be that your input is 5.1 and libvo_aacenc only supports stereo.

So either use a different encoder or downmix (-ac 2) or don't transcode audio at all (-c:a copy).