[libav-bugs] [Bug 693] New: Avconv buffers a lot of input before producing any output

bugzilla at libav.org bugzilla at libav.org
Wed May 28 09:49:14 CEST 2014


https://bugzilla.libav.org/show_bug.cgi?id=693

           Summary: Avconv buffers a lot of input before producing any
                    output
           Product: Libav
           Version: 9
          Platform: All
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: utilities
        AssignedTo: bugzilla at libav.org
        ReportedBy: aizvorski at gmail.com


I'm using avconv as part of a pipeline, like this:

(command that outputs a raw h264 file to stdout) | avconv -y -f h264 -r 24 -i -
-r 24 -vcodec copy -f mp4 output.mp4

There is no data written to output.mp4 for a variable amount of time, it could
be 50-80 seconds, and then the avconv writes the whole beginning of the video
very fast.  

Avconv prints out this:

avconv version 9.13-6:9.13-1+rpi1, Copyright (c) 2000-2014 the Libav developers
  built on May 11 2014 01:14:19 with gcc 4.8 (Raspbian 4.8.2-16)
[h264 @ 0xccb260] Estimating duration from bitrate, this may be inaccurate
Input #0, h264, from 'pipe:':
  Duration: N/A, bitrate: N/A
    Stream #0.0: Video: h264 (High), yuv420p, 864x648, 24 fps, 24 tbr, 24 tbn
Output #0, mp4, to 'output.mp4':
  Metadata:
    encoder         : Lavf54.20.4
    Stream #0.0: Video: libx264, yuv420p, 864x648, q=2-31, 24 tbn, 24 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press ctrl-c to stop encoding
...
video:5653kB audio:0kB global headers:0kB muxing overhead 0.326568%
Received signal 2: terminating.

The line "Estimating duration from bitrate" and the rest are printed only after
buffering is complete and it has started writing its output.

To test this from any input file, use "mbuffer -i input.h264 -r 10K" as the
command that outputs a h264 file.

Expected behavior: one frame in, one frame out :)

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