[MPlayer-users] hrtf with -ao channels or with -channels

[Alessandro Pezzoni]

Hello,
recently I tried to play a video with 6 channels audio, at 48 Khz,
through hrtf (with mplayer svn revision 34089).
Invoking mplayer with
$ mplayer -channels 6 -af hrtf video.mp4
as suggested in the docs [1] results in audio artifacts when playing
certain sounds, like explosions or engine roars.

Invoking mplayer with
$ mplayer -af channels=6:hrtf video.mp4
works as expected.


Here is mplayer's output in the first case:

MPlayer SVN-r34089-4.6.1 (C) 2000-2011 MPlayer Team
163 audio & 364 video codecs

Playing video.mp4.
libavformat file format detected.
[lavf] stream 0: video (h264), -vid 0
[lavf] stream 1: audio (aac), -aid 0, -alang und
VIDEO:  [H264]  1280x528  24bpp  23.976 fps  1475.6 kbps (180.1 kbyte/s)
Clip info:
 major_brand: isom
 minor_version: 1
 compatible_brands: isomavc1
 creation_time: 2011-05-15 18:58:16
Load subtitles in ./
==========================================================================
Forced video codec: ffmpeg12vdpau
Forced video codec: ffwmv3vdpau
Forced video codec: ffvc1vdpau
Forced video codec: ffh264vdpau
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffh264vdpau] vfm: ffmpeg (FFmpeg H.264 (VDPAU))
==========================================================================
==========================================================================
Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders
AUDIO: 48000 Hz, 6 ch, s16le, 223.6 kbit/4.85% (ratio: 27947->576000)
Selected audio codec: [ffaac] afm: ffmpeg (FFmpeg AAC (MPEG-2/MPEG-4 Audio))
==========================================================================
AO: [alsa] 48000Hz 2ch s16le (2 bytes per sample)
Starting playback...
[hrtf] Using HRTF to mix 5 discrete surround into L, R channels
[VD_FFMPEG] Trying pixfmt=0.
Movie-Aspect is 2.42:1 - prescaling to correct movie aspect.
VO: [vdpau] 1280x528 => 1280x528 H.264 VDPAU acceleration
[VD_FFMPEG] XVMC-accelerated MPEG-2.
A:   1.1 V:   1.1 A-V: -0.004 ct: -0.038   0/  0 10%  1% 11.0% 1 0

Exiting... (Quit)


And here is the output in the second case:

MPlayer SVN-r34089-4.6.1 (C) 2000-2011 MPlayer Team
163 audio & 364 video codecs

Playing video.mp4.
libavformat file format detected.
[lavf] stream 0: video (h264), -vid 0
[lavf] stream 1: audio (aac), -aid 0, -alang und
VIDEO:  [H264]  1280x528  24bpp  23.976 fps  1475.6 kbps (180.1 kbyte/s)
Clip info:
 major_brand: isom
 minor_version: 1
 compatible_brands: isomavc1
 creation_time: 2011-05-15 18:58:16
Load subtitles in ./
==========================================================================
Forced video codec: ffmpeg12vdpau
Forced video codec: ffwmv3vdpau
Forced video codec: ffvc1vdpau
Forced video codec: ffh264vdpau
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffh264vdpau] vfm: ffmpeg (FFmpeg H.264 (VDPAU))
==========================================================================
==========================================================================
Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders
AUDIO: 48000 Hz, 6 ch, s16le, 223.6 kbit/4.85% (ratio: 27947->576000)
Selected audio codec: [ffaac] afm: ffmpeg (FFmpeg AAC (MPEG-2/MPEG-4 Audio))
==========================================================================
AO: [alsa] 48000Hz 6ch floatle (4 bytes per sample)
Starting playback...
[VD_FFMPEG] Trying pixfmt=0.
Movie-Aspect is 2.42:1 - prescaling to correct movie aspect.
VO: [vdpau] 1280x528 => 1280x528 H.264 VDPAU acceleration
[VD_FFMPEG] XVMC-accelerated MPEG-2.
A:   1.8 V:   1.8 A-V: -0.000 ct: -0.041   0/  0  5%  0%  0.8% 0 0

Exiting... (Quit)


I'm writing here because I don't know if this is expected behaviour or a bug.
Hope it helps, anyway.

Alessandro

[1] http://www.mplayerhq.hu/DOCS/HTML/en/advaudio-surround.html

-- 
If God had intended for email to be written in HTML, then the
traditional signoff of prayers would be </amen> -- Tom Liston