dropped frames when using compand with overlay

[Elon Musk]

Buffer queue overflow does not happen if delay for compand is set to 0.

> ffmpeg -i ~/matrixbench_mpeg2.mpg -f lavfi -i color=pink -lavfi "overlay" -af "compand=attacks=5:decays=10:volume=-20:points=-90/-90|-40/-20|0/-10:delay=5" -c:v ffv1 /tmp/o.nut
ffmpeg version N-69783-ge4a6486 Copyright (c) 2000-2015 the FFmpeg developers
  built with FreeBSD clang version 3.3 (tags/RELEASE_33/final 183502) 20130610
  configuration: --extra-cflags=-I/usr/local/include --extra-ldflags=-L/usr/local/lib --as=clang --cc=clang --disable-debug --disable-ffserver --disable-indevs --disable-outdevs --disable-static --enable-gpl --enable-indev=x11grab_xcb --enable-indev=lavfi --enable-indev=oss --enable-nonfree --enable-openssl --enable-outdev=oss --enable-shared --enable-stripping --enable-x11grab --enable-libfreetype --enable-libx264 --enable-libxvid --enable-libmp3lame --enable-ladspa --enable-frei0r --mandir=/usr/local/man --samples=../fate-suite
  libavutil      54. 18.100 / 54. 18.100
  libavcodec     56. 22.100 / 56. 22.100
  libavformat    56. 21.100 / 56. 21.100
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 11.100 /  5. 11.100
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
[NULL @ 0x2a059800] start time for stream 0 is not set in estimate_timings_from_pts
Input #0, mpeg, from '/home/r/matrixbench_mpeg2.mpg':
  Duration: 00:03:07.66, start: 0.220000, bitrate: 5633 kb/s
    Stream #0:0[0x1bf]: Data: dvd_nav_packet
    Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, bt470bg/bt470m/bt470m), 720x576 [SAR 16:15 DAR 4:3], max. 11421 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0:2[0x1c0]: Audio: mp2, 48000 Hz, stereo, s16p, 384 kb/s
Input #1, lavfi, from 'color=pink':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #1:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 320x240 [SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc
File '/tmp/o.nut' already exists. Overwrite ? [y/N] y
Output #0, nut, to '/tmp/o.nut':
  Metadata:
    encoder         : Lavf56.21.100
    Stream #0:0: Video: ffv1 (FFV1 / 0x31564646), yuv420p, 720x576 [SAR 16:15 DAR 4:3], q=2-31, 200 kb/s, 25 fps, 51200 tbn, 25 tbc (default)
    Metadata:
      encoder         : Lavc56.22.100 ffv1
    Stream #0:1: Audio: mp3 (libmp3lame) (U[0][0][0] / 0x0055), 48000 Hz, stereo, s32p
    Metadata:
      encoder         : Lavc56.22.100 libmp3lame
Stream mapping:
  Stream #0:1 (mpeg2video) -> overlay:main (graph 0)
  Stream #1:0 (rawvideo) -> overlay:overlay (graph 0)
  overlay (graph 0) -> Stream #0:0 (ffv1)
  Stream #0:2 -> #0:1 (mp2 (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
[Parsed_overlay_0 @ 0x2a00dee0] [framesync @ 0x2a1012a4] Buffer queue overflow, dropping.
    Last message repeated 17 times
[Parsed_overlay_0 @ 0x2a00dee0] [framesync @ 0x2a1012a4] Buffer queue overflow, dropping.
    Last message repeated 46 times
[Parsed_overlay_0 @ 0x2a00dee0] [framesync @ 0x2a1012a4] Buffer queue overflow, dropping.
frame=   64 fps= 15 q=0.0 Lsize=    5230kB time=00:00:02.61 bitrate=16370.5kbits/s    
video:5184kB audio:41kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.080791%

[Elon Musk]

Fixed.