[MPlayer-users] FFMpeg or MEncoder ODML problem

[Francois Visagie]

> -----Original Message-----
> From: mplayer-users-bounces at mplayerhq.hu 
> [mailto:mplayer-users-bounces at mplayerhq.hu] On Behalf Of 
> Heimdall Midgard
> Sent: 18 June 2006 21:59
> To: MPlayer Users
> Subject: [MPlayer-users] FFMpeg or MEncoder ODML problem
> 
> The problem I'm about to describe involves either ffmpeg or 
> mplayer. Since both projects are hosted at mplayerhq.hu, I'm 
> reporting this here first in the hope that this is not a bug 
> but a simple configuration issue.
> 
> The problem is with OpenDML AVIs encoded by MEncoder using 
> certain audio/video codec combinations. There's an "echoing"
> effect in the audio of the OpenDML AVIs when I play them 
> using ffplay. The effect can also be heard in videos 
> re-encoded from the OpenDML AVIs via the ffmpeg libraries 
> (for example, by using the third party program ffmpeg2theora).
> 
> The command I use to produce the OpenDML AVIs is:
> 
> mencoder -vf eq2=1:1:-0.02:1,hqdn3d=8:16:6,pp=h1/v1,harddup 
> -ovc lavc -lavcopts vcodec=ffvhuff:vstrict=-2 -oac pcm -o 
> output.avi input.avi
> 
> The input AVIs have the following properties (mplayer -identify):
> 
> ID_DEMUXER=avi
> ID_VIDEO_FORMAT=DIVX
> ID_VIDEO_BITRATE=2625512
> ID_VIDEO_WIDTH=608
> ID_VIDEO_HEIGHT=448
> ID_VIDEO_FPS=12.000
> ID_VIDEO_ASPECT=0.0000
> ID_AUDIO_FORMAT=8192
> ID_AUDIO_BITRATE=96000
> ID_AUDIO_RATE=0
> ID_AUDIO_NCH=0
> 
> Apparently the "echoing" effect only occurs with AVIs I 
> encode using a combination of PCM and a low compression video 
> codec like ffvhuff, ffv1 or huffyuv. I realize that ffvhuff 
> and ffv1 are experimental codecs. However the problem also 
> occurs with AVIs encoded using PCM and huffyuv.
> 
> The "echoing" effect does not occur: (1) if I encode without 
> OpenDML or (2) if I encode using high compression codecs like
> MPEG4 or AC3.
> 
> Is this an FFMpeg or an MPlayer problem? Any suggestions or fixes?

Hi Heimdall,

Not being familiar with mencoder, I'd like to offer you some general advice
anyway. Does your problem audio really have an echo, or does it sound
hollow? If hollow, it's often caused by too low a sampling rate when you
convert from one format to another.

As a rule of thumb, bear in mind that to preserve quality with lossless
conversion, the sampling rate needs to be twice the bandwidth of the input
audio. When doing lossy compression, run tests starting with such a sampling
rate and gradually reduce it until you reach the optimal point to your
liking.

Regards,
Francois





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