[FFmpeg-devel] grabbing from dv1394
Tommi Sakari Uimonen
tuimonen
Wed Jun 6 00:58:54 CEST 2007
>> I got the dv1394 grabbing working with a patch from
>> http://svn.pardus.org.tr/pardus/devel/applications/multimedia/ffmpeg/files/ffmpeg-dv1394.patch
>>
>> I grab with:
>>
>> ./ffmpeg -f dv1394 -i /dev/dv1394/0 -f avi -acodec copy -vcodec copy -y
>> outfile.avi
> You should always post the *complete* output messages. In this case, it
> would have told us the actual containers, codecs, sizes, ...
For first grabbing test, I mount my disk with -o remount,sync. The result
being that only 7 frames get written of about 30 seconds of running.
tuimonen at punttu:~/incoming/ffmpeg$ ./ffmpeg -f dv1394 -i /dev/dv1394/0 -f
avi -acodec copy -vcodec copy -y outfile.avi
FFmpeg version SVN-r9225, Copyright (c) 2000-2007 Fabrice Bellard, et al.
configuration: --enable-gpl --enable-pthreads --enable-x11grab
--enable-dc1394 --enable-liba52 --enable-liba52bin --enable-libfaac
--enable-libfaad --enable-libfaadbin --enable-libmp3lame --enable-libogg
--enable-libtheora --enable-libvorbis --enable-xvid
libavutil version: 49.4.0
libavcodec version: 51.40.4
libavformat version: 51.12.1
built on Jun 6 2007 00:52:53, gcc: 4.1.2 (Ubuntu 4.1.2-0ubuntu4)
Input #0, dv1394, from '/dev/dv1394/0':
Duration: N/A, start: 0.000000, bitrate: 30336 kb/s
Stream #0.0: Video: dvvideo, yuv420p, 720x576, 28800 kb/s, 25.00 fps(r)
Stream #0.1: Audio: pcm_s16le, 48000 Hz, stereo, 1536 kb/s
Output #0, avi, to 'outfile.avi':
Stream #0.0: Video: dvvideo, yuv420p, 720x576, q=2-31, 28800 kb/s, 25.00
fps(c)
Stream #0.1: Audio: pcm_s16le, 48000 Hz, stereo, 1536 kb/s
Stream mapping:
Stream #0.0 -> #0.0
Stream #0.1 -> #0.1
Press [q] to stop encoding
frame= 7 fps= 0 q=0.0 Lsize= 1939kB time=0.2 bitrate=66192.5kbits/s
video:984kB audio:45kB global headers:0kB muxing overhead 88.389496%
So back to the async (-o remount,async):
tuimonen at punttu:~/incoming/ffmpeg$ ./ffmpeg -f dv1394 -i /dev/dv1394/0 -f
avi -acodec copy -vcodec copy -y outfile.avi
FFmpeg version SVN-r9225, Copyright (c) 2000-2007 Fabrice Bellard, et al.
configuration: --enable-gpl --enable-pthreads --enable-x11grab
--enable-dc1394 --enable-liba52 --enable-liba52bin --enable-libfaac
--enable-libfaad --enable-libfaadbin --enable-libmp3lame --enable-libogg
--enable-libtheora --enable-libvorbis --enable-xvid
libavutil version: 49.4.0
libavcodec version: 51.40.4
libavformat version: 51.12.1
built on Jun 6 2007 00:52:53, gcc: 4.1.2 (Ubuntu 4.1.2-0ubuntu4)
Input #0, dv1394, from '/dev/dv1394/0':
Duration: N/A, start: 0.000000, bitrate: 30336 kb/s
Stream #0.0: Video: dvvideo, yuv420p, 720x576, 28800 kb/s, 25.00 fps(r)
Stream #0.1: Audio: pcm_s16le, 48000 Hz, stereo, 1536 kb/s
Output #0, avi, to 'outfile.avi':
Stream #0.0: Video: dvvideo, yuv420p, 720x576, q=2-31, 28800 kb/s, 25.00
fps(c)
Stream #0.1: Audio: pcm_s16le, 48000 Hz, stereo, 1536 kb/s
Stream mapping:
Stream #0.0 -> #0.0
Stream #0.1 -> #0.1
Press [q] to stop encoding
frame= 706 fps= 23 q=0.0 Lsize= 231315kB time=28.2
bitrate=67196.2kbits/s
video:99281kB audio:5288kB global headers:0kB muxing overhead 121.208528%
I don't get the bitrate 67196.2kbits/s, since the input data is only
(28800+1536)*1000 bits/s. It's over twice the input rate.
And the fps, being 24 just before I hit q and the encoding stopped, but
source is 25 fps.
Could it have something to do with 25fps not being defined (from
dc1394.c):
struct dc1394_frame_rate {
int frame_rate;
int frame_rate_id;
} dc1394_frame_rates[] = {
{ 1875, FRAMERATE_1_875 },
{ 3750, FRAMERATE_3_75 },
{ 7500, FRAMERATE_7_5 },
{ 15000, FRAMERATE_15 },
{ 30000, FRAMERATE_30 },
{ 60000, FRAMERATE_60 },
{ 0, FRAMERATE_30 } /* default -- gotta be the last one */
};
and later in static int dc1394_read_header(AVFormatContext *c,
AVFormatParameters * ap)
for (fps = dc1394_frame_rates; fps->frame_rate; fps++)
if (fps->frame_rate == av_rescale(1000, ap->time_base.den,
ap->time_base.num))
break
>> I have also tried to pipe dvgrab output to ffmpeg, but never figured out
>> the right way to do it. I tried for instance
>>
>> dvgrab --format dv1 - | ffmpeg -i - -acodec copy -sameq -y outfile.avi
>>
>> but I got 'pipe:: could not find codec parameters' error.
>
> Again, without the full output...
dvgrab pipe with dv2 output format:
tuimonen at punttu:~/incoming/ffmpeg$ dvgrab --format dv2 - | ./ffmpeg -i -
-acodec copy -sameq -y outfile.avi
FFmpeg version SVN-r9225, Copyright (c) 2000-2007 Fabrice Bellard, et al.
configuration: --enable-gpl --enable-pthreads --enable-x11grab
--enable-dc1394 --enable-liba52 --enable-liba52bin --enable-libfaac
--enable-libfaad --enable-libfaadbin --enable-libmp3lame --enable-libogg
--enable-libtheora --enable-libvorbis --enable-xvid
libavutil version: 49.4.0
libavcodec version: 51.40.4
libavformat version: 51.12.1
built on Jun 6 2007 00:52:53, gcc: 4.1.2 (Ubuntu 4.1.2-0ubuntu4)
Capture Started
pipe:: Unknown format
with raw output format:
tuimonen at punttu:~/incoming/ffmpeg$ dvgrab --format raw - | ./ffmpeg -i -
-acodec copy -sameq -y outfile.avi
FFmpeg version SVN-r9225, Copyright (c) 2000-2007 Fabrice Bellard, et al.
configuration: --enable-gpl --enable-pthreads --enable-x11grab
--enable-dc1394 --enable-liba52 --enable-liba52bin --enable-libfaac
--enable-libfaad --enable-libfaadbin --enable-libmp3lame --enable-libogg
--enable-libtheora --enable-libvorbis --enable-xvid
libavutil version: 49.4.0
libavcodec version: 51.40.4
libavformat version: 51.12.1
built on Jun 6 2007 00:52:53, gcc: 4.1.2 (Ubuntu 4.1.2-0ubuntu4)
Capture Started
pipe:: could not find codec parameters
> You are writing raw video to file. That eats a lot of I/O resources, and
> a large fraction of that use will be concentrated in bursts - which will
> interfere with the interrupts from the TV card.
Raw dv in PAL format and 48kHz stereo wav is roughly 4MB/s (estimated up).
Even old IDE harddisks can cope with this. My old AthlonXP was able to
grab 90min dv (using dvgrab) without one single frame lost.
AFAIK, Firewire was designed not to be 'bursty' (like USB is), but to
guarantee steady data stream. Of course I'm just waving hands and I
really don't know the internals of the implementation. And even if
firewire gives steady flow, the other resources might be on the bursty
side of the road.
> There are various ways: patch ffmpeg so that there is an fsync after
> every write; or a sync(2) after every frame write; or a separate process
> that does a sync(2) every second; or write to a partition that is
> mounted with -o sync.
The sync may not be the answer here, as it proved to be extremely slow.
And dvgrab performs fine on async filesystem, that rules out the I/O
resource issues.
I haven't yet browsed the code enough to see if the grabbing and writing
to disk are done in separate threads. At least in audio grabbing
(Ardour,ecasound and other decent hd recorders) it is a must that the disk
thread and audio thread are separated. Otherwise it will result to audio
dropouts.
Maybe I should also dig into the dvgrab code to see what it does
differently.
Tommi
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