test
[libav.git] / doc / ffmpeg.txt
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1* ffmpeg can use YUV files as input :
2
3 ffmpeg /tmp/out.mpg /tmp/test
4
5If will use the files:
6/tmp/test0.Y, /tmp/test0.U, /tmp/test0.V,
7/tmp/test1.Y, /tmp/test1.U, /tmp/test1.V, etc...
8
9The Y files use twice the resolution of the U and V files. They are
10raw files, without header. They can be generated by all decent video
11decoders.
12
13* ffmpeg can use a video4linux compatible video source :
14
15 ffmpeg /tmp/out.mpg
16
17 Note that you must activate the right video source and channel
18 before launching ffmpeg. You can use any TV viewer such as xawtv by
19 Gerd Knorr which I find very good.
20
21* There are some importants options to know:
22
23-s size set frame size [160x128]
24-f format set encoding format [mpeg1]
25-r fps set frame rate [25]
26-b bitrate set the bitrate in kbit/s [100]
27-t time set recording time in seconds [10.0]
28
29The frame size can also be: cif, qcif, sqcif and 4cif.
30The encoding format can be mpeg1, h263 or rv10.
31
32Advanced options are:
33
34-d device set video4linux device name
35-g gop_size set the group of picture size.
36 An 'intra' frame is generated every gop_size frames.
37-i use only intra images (speed up compression, but lower quality).
38-c comment set the comment string.
39
40Comment strings are only used for Real Video(tm) encoding. Tags are
41used in the comment string. A typical comment string is:
42
43"+title=Test Video +author=FFMpeg +copyright=Free +comment=Generated by FFMpeg 1.0"
44
45The output file can be "-" to output to a pipe. This is only possible
46with mpeg1 and h263 formats.
47
48* Tips:
49
50- For low bit rate application, use a low frame rate and a small gop
51 size. This is especially true for real video where the Linux player
52 does not seem to be very fast, so it can miss frames. An example is:
53
54 ffmpeg -g 3 -r 3 -t 10 -b 50 -s qcif -f rv10 /tmp/b.rm
55
56- The parameter 'q' which is displayed while encoding is the current
57 quantizer. The value of 1 indicates that a very good quality could
58 be achieved. The value of 31 indicates the worst quality. If q=31
59 too often, it means that the encoder cannot compress enough to meet
60 your bit rate. You must either increase the bit rate, decrease the
61 frame rate or decrease the frame size.
62