ffmpeg at half speed ... sort of.
Paul Chvostek
paul+fbsd at it.ca
Sun Feb 6 19:28:44 PST 2005
This is weird. When I encode with ffmpeg, the resultant file appears to
play back at about half the expected framerate, with the wrong bitrate.
I encode with ffmpeg:
encode$ ffmpeg -y -an -vd /dev/bktr0 -s 160-120 -tvstd ntsc \
-vcodec mpeg4 -b 50 -f avi -t 15 -r 29.97 test.avi
And the resultant file appears to be right:
encode$ file test.avi
test.avi: RIFF (little-endian) data, AVI, 160 x 120, ~30 fps, video: DivX 4
And mplayer says:
play$ mplayer test.avi 2>/dev/null | grep VIDEO
VIDEO: [DIVX] 160x120 24bpp 29.970 fps 127.9 kbps (15.6 kbyte/s)
Note the 127.9 kbps. That's at odds with ffmpeg's "-b 50". And the
actual video that gets displayed seems to run in slow motion. Yet after
playing a 15 second clip, mplayer shows:
V: 15.0 450 1% 3% 0.0% 0 0 0%
indicating 30fps. The video plays back in real time when I force the
framerate to the ratio of 127.9 kbps to the 50 I specified:
encode$ mplayer -fps 77 test.avi
But that doesn't give me 15 seconds of video.
Specs for the encoder and player are:
encode$ uname -sr
FreeBSD 5.3-STABLE
encode$ dmesg | grep bktr0:
bktr0: <BrookTree 878> mem 0xee3fe000-0xee3fefff irq 21 at device 10.0 on pci1
bktr0: [GIANT-LOCKED]
bktr0: Warning - card vendor 0x0000 (model 0x0000) unknown.
bktr0: Detected a DPL34193 at 0x84
bktr0: Intel Smart Video III/VideoLogic Captivator PCI, dpl3518a dolby.
play$ mplayer --version
MPlayer 1.0pre5try2-3.4.2 (C) 2000-2004 MPlayer Team
...
The card is an AVerMedia unit with no tuner or audio, despite what it
claims. Mplayer doesn't have problems with anything else.
Anybody know what the heck is going on here?
Thanks. :)
--
Paul Chvostek <paul at it.ca>
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