mjpegtools.1

来自「Motion JPEG编解码器源代码」· 1 代码 · 共 2,296 行 · 第 1/5 页

.IP "-P"
.nr bi 1

.PP
This ensures that 2 B frames appear between adjacent I/P
frames. Several common MPEG-1 decoders can't handle streams that do not
have 2 B-frames between I/P frames
.IP "-g 6 -G 20"
.nr bi 1

.PP
the encoder can dynamically change the
group-of-pictures size to reflect scene changes. This is done by setting a
maximum GOP (-G flag) size larger than the minimum (-g flag).   
For VCDs sensible values might be a minimum of 9 and a maximum of 15.
For SVCD 9 and 15 would be good values. If you only want to play it   
back on SW player you can use other min-max values.
.if \n(ll>1 .RE
.nr ll -1

.PP

.PP
Example

.PP
\fB> lav2yuv stream*.avi \(br mpeg2enc -b 1500 -r 16 -4 1 -2 1
-S 630 -B 260 -o video_n1_1500_r16_41_21_S630_B240.m1v\fP

.PP
lav2yuv processes all the stream files. Then mpeg2enc is given some
options that make the encoded stream look nicer. Using
\fB-S 630\fP means that mpeg2enc marks the stream so that mplex
generates a new stream every 630MB. One important thing is the use of
the \fB-B\fP option which specifies the non-video (audio and mplex
information) bitrate. The \fB-B\fP value of 260 should be fine for audio   
with 224kBit and mplex information. For further information take a  
look at the encoding scripts in the scripts directory.

.PP

.PP
MPEG1 Multiplexing Example


.PP
Example

.PP
\fB >mplex sound.mp2 video.m1v -o my_video.mpg\fP

.PP
Puts the sound.mp2 and the video.m1v stream together to my_video.mpg.
It only works that easy if you have CBR (the -q option was not used with
mpeg2enc).

.PP
Example

.PP
\fBmplex -V -r 1740 audio.mp2 video_vbr.m1v -o vbr_stream.mpg\fP

.PP
Here we multiplex a variable bitrate stream. mplex is now a single
pass multiplexer so it can't detect the maximal bitrate and we have to
specify it. The data rate for the output stream is: \fBaudio bitrate +
peak videobitrate + 1-2% for mplex information\fP\&. If audio (-b 224)
has 224kBit, video has 1500kBit (was encoded with -b 1500 -q 9) then we   
have 1724 * 1.01 or about 1740kBit.

.PP
.SH Creating MPEG2 Videos


.PP
MPEG2 is recommended for sources with a greater picture than 352x240
for NTSC and 352x288 for PAL. MPEG2 can also handle interlaced sources
like recording from TV at full resolution.

.PP
MPEG2 allows the usage of mpeg layer 3 (mp3) sound. So you can use   
your favorite mp3encoder for the creation of the sound.  However, MP3 audio 
is not valid for DVDs.  It is best to use MP2 (Layer 2) audio.  The audio 
can also be a VBR Stream.

.PP
MPEG2 is usually a VBR Stream. MPEG2 creation with optimization requires a
lot of CPU power.  A film with the double resolution is NOT
4 times larger than an MPEG1 Stream. Depending on your quality
settings it will be about 1.5 up to 3 times larger than the MPEG1
Stream at its lower resolution.

.PP
MPEG2 Audio creation Example


.PP
\fB> lav2wav editlist.eli \(br mp2enc -o sound.mp2\fP

.PP
This will fit the MPEG2 quite well. You can save some bits by telling
mp2enc to use a lower bitrate (-b option) like 160 or 192 kBit/s. And might
want to add -r 44100 so that mpeg2enc generates a 44.1kHz sampling rate audio
file. I hope I don't need to explain the usage of an MP3 Encoder.
But you should not use all the fancy options that are available.

.PP
MPEG2 Video creation Example


.PP
\fB> lav2yuv editlist.eli \(br mpeg2enc -f 3 -b 3000 -q 9
-o video.m2v\fP

.PP
A very simple example for MPEG2 Video.
The most important option is the -f 3. That tells mpeg2enc that it
should create a MPEG2 stream. Because it is a generic MPEG2 you have
to use the -b bitrate options. And should use the -q option because
you usually want a space saving VBR Stream. When using VBR streams the
-b option tells mpeg2enc the maximum bitrate that can be used. The -q  
option tell mpeg2enc what quality the streams should have.  The bitrate has
an upper bound of the value specified by -b.

.PP
\fB> lav2yuv editlist.eli \(br mpeg2enc -f 3 -4 1 -2 1 -q7 -b 4500
-V 300 -P -g 6 -G 18 -I 1 -o video.m2v\fP

.PP
This will generate a higher quality MPEG2 stream because the -4 1 and
-2 1 options were used.  With -b 4500 -q 7 you tell mpeg2enc the 
maximal bitrate and the quality factor.  -V is the video buffer size
used for decoding the stream. For SW playback it can be much higher
than the default. Dynamic GOP is set with -g and -G.  A larger GOP size can
help reduce the bit-rate required for a given quality but very large sizes
can introduce artifacts due to DCT/iDCT accumulated rounding errors.
The -P option
also ensures that 2 B frames appear between adjacent I/P frames. The
-I 1 option tells mpeg2enc that the source is a interlaced material
like videos. There is (time consuming) interlaced motion
compensation logic present in mpeg2enc.  Mpeg2enc will use that logic
if the size of the frames you encode is larger than the VCD size for  
your TV Norm.

.PP
If you denoise the images with yuvdenoise and use the deinterlacing  
(-F) option you should tell mpeg2enc that it does not need to 
do motion estimation for interlaced material. You have to use the -I 0
option of mpeg2enc to say that the frames are already deinterlaced.
This will save a lot of time when encoding. If you don't use -I 0 it will
not cause problems, the encoding will just take longer.

.PP
You can also use scaling an options that optimize (denoise) the 
images to get smaller streams.  These options are explained in detail
in the following sections.Which values should be used for VBR Encoding


.PP
The -q option controls the minimum quantization of the output stream.
Quantization controls the precision with which image information is
encoded. The lower the value the better the image quality.  Values below 4
are extremes and should only be used if you know what you are doing

.PP
Usually you have to set up a maximum bitrate with the -b option.
The tricky task is to set a value for the -q option and the -b option
that produces a nice movie without using too much bandwidth and does not 
introduce too many artifacts.

.PP
A quality factor should be chosen that way that the mplex output of
Peak bit-rate and average bit-rate differ by about 20-25%\&.
If the difference is very small (less than < 10%) it is likely
that you will begin to see artifacts in high motion scenes.  The most common
cause of the average rate being too close (or equal) to the maximum rate
is wrong value for the maximal bitrate or a quality factor that is too 
high.

.PP
A combination that will produce more artifacts than you can count is a  
SVCD with a maximal video bitrate of 2500kBit and a qualitfactor set
to 1 or 2.
For SVCD with a video limit of 2500kBit a quality factor of 7-11 fits
quite good (8 is the default). If you use filter programs or have a very 
good source like digital TV, DVD like material or rendered pictures you can
use a quality factor of 6 when creating SVCDs.  If your SVCD/DVD
player supports higher bitrates than the official 2788kBit/sec for the
video and audio.   When using a higher bitrate and quality factor
action scenes will look much better but of course the playing time of the
disc will be less.

.PP
The same (7-11) quality factor for a full size picture and a top
bitrate of 3500 to 4000 kBit will produce few artifacts.

.PP
For SVCD/DVD you can expect a result like the one described if the
maximal bitrate is not set too low:

.PP

.DS
.sp 
.ft RR
.nf
   q <= 6 real sharp pictures, and good quality
   q <= 8 good quality
   q >= 10 average quality
   q >= 11 not that good
   q >= 13 here even still sequences might look blocky
.DE
.fi 
.ec
.ft P
.sp
Encoding destination TV (interlaced) or Monitor (progressive)


.PP
MPEG2 supports interlaced data in addition to the progressive format. 
A MPEG2 movie can be interlaced or progressive. It depends on the source 
(film or broadcast) and on the viewing device.

.PP
If you encode a film both fields should be the same. Deinterlace the
stream with yuvdenoise -F, or if you have a high quality source, and  
don't need to use the denoiser, with yuvcorrect -T NOT_INTERLACED. Also
set the mpeg2enc interlace-mode (-I) option to 0. This means that
there is no interlacing.
We do not really need deinterlacing here because there is no motion 
between the fields of the frame. We only need to unite the two fields into a
single progressive frame.

.PP
This movie should play back an any device (TV or Monitor) without
problems.

.PP
If you have an interlaced source (broadcast) you can encode it as     
interlaced stream. Or deinterlace the stream and encode it as
progressive stream. If you deinterlace it with yuvdenoise -F, you will
lose details.
But if you plan to play the recorded stream on your DVD player and your
TV it would not be wise to perform deinterlacing.  If you only want to play it
back on the Monitor (progressive display) the picture looks better
when playing it back if it is deinterlaced. If the player you use can
do deinterlacing it does not matter if your encoded video has
interlaced frames or progressive frames.

.PP
If you plan to deinterlace the stream you can only do this with
yuvdenoise -F, and set the mpeg2enc -I 0. If you do not want to
deinterlace the stream you do not need to set any special option (do
not use yuvdenoise -F and mpeg2enc -I 0)

.PP
If you like to pause the stream and look on the still you should
deinterlace. Because then the image is flicker free when pausing.

.PP
If you have a film (progressive) with parts from a broadcast
(interlaced) mixed together (like in a documentary where some parts
from a speaker are recorded interlaced and other parts are filmed)
you have to choose between good film sequences with average still images
or average looking film sequences with good still images.

.PP
For good film with average stills do not deinterlace.  For average film 
sequences with good stills then deinterlace (using -F and -I 0).

.PP
MPEG2 Multiplexing Example


.PP
\fB> mplex -f 3 -b 300 -r 4750 -V audio.mp3 video.mp3 -o final.mpg\fP

.PP
Now both streams (a mp3 audio and a mpeg2 video) are multiplex into a 
single stream (final.mpg). You  
have to use the -f 3 option to tell mplex the output format. You also
have to add the -b decoder buffers size with the same value used when 
encoding the video. -r is that rate of video + audio +1-2% of mplex
information.

.PP
The -V option tells that your source for mplexing is a VBR stream. If
you don't use this option mplex creates something like a CBR Stream
with the bitrate you have told it with the -r option.  These streams  are
usually get BIG.

.PP

.PP
.SH Creating Video-CD's


.PP
VCD is a constrained version of MEPG1 streams.
VCD format was defined by Philips. The goal was to use a single speed
CD-drive and other cheap hardware (not flexible) to have a
cheap HW-Player.  Because of that there are some limitations on VCD's.
The bitrate for video is 1152kBit and for audio layer 2 audio 224kBit stereo.
You are not allowed to use the -q option, dynamic GOP sizes and the video 
buffer is limited to 46kB.
The image size is limited to 352x240 for NTSC, an to 352x288 for PAL.

.PP
If you have no VCD (only) player and you plan to use your DVD 
player then it is quite possible that the DVD player will be 
flexible enough to allow higher bitrates, dynamic GOP sizes, larger video 
buffer and so on

.PP
VCD Audio creation Example


.PP
\fB> lav2wav stream.avi \(br mp2enc -V -o sound.mp2\fP

.PP
\fB-V\fP force VCD 2.0 compatible output.
There the audio samplerate is fixed to 44.1kHz. And  you can choose the audio
bitrate for mono audio to be 64, 96 or 192kBit/sec. If you have stereo audio 
you can choose 128, 192, 224 or 384kBit/sec. 
For hardware players, you should stick to 44.1 224kBps Stereo layer 2 Audio.

.PP
VCD Video creation Example


.PP
\fB> lav2yuv stream.avi \(br yuvscaler -O VCD \(br
mpeg2enc -f 1 -r 16 -o video.mpg\fP

.PP
For a VCD compatible output the -f 1 sets all options in mpeg2enc as
needed. It seems that many VCD players (Avex for example) are not able to
play MPEG streams that are encoded with a search radius greater than 16 so
do not use the -r option to override the default of 16.

.PP
\fB> lav2yuv streams.eli \(br
mpeg2enc -f 1 -4 1 -2 1 -S 630 -B 260 -P -o video.m1v\fP

.PP
Using \fB'-S 630'\fP means that mpeg2enc marks the stream so
that mplex generates a new stream every 630MB. One important thing is the use
of the \fB-B\fP option which specifies the non-video (audio and mplex
information) bitrate. The -B value of 260 should be fine for audio
with 224kBit and mplex information. For further information take a   
look at the encoding scripts in the scripts directory. So the
multiplexed streams should easily fit on a CD with 650MB.

.PP
The default value (-B) is 700MB for the video. mpeg2enc marks
automatically every stream at that size if the -B option is not used to set
a different value.  If you have a CD where you can write more data (perhaps
as much as 800MB), you have to set the -S option or otherwise mpeg2enc will 
mark the stream at 700 MB, and mplex will split the stream there. 
Which is almost certainly not what you want.

.PP

.PP

.PP
VCD Multiplexing Example


.PP
\fB> mplex -f 1 sound.mp2 video.mpg -o vcd_out.mpg\fP

.PP
The -f 1 option turns on a lot of weird stuff that otherwise has no
place in a respectable multiplexer!

.PP
Creating the CD


.PP
The multiplexed streams have to be converted to an VCD compatible.  
This is done by vcdimager

.PP

.PP
\fB> vcdimager testvideo.mpg\fP

.PP
Creates a \fBvideocd.bin\fP, the data file, and a \fBvideocd.cue\fP
which is used as control file for cdrdao.

.PP
You use cdrdao to burn the image. Cdrdao is yet another fine
Sourceforge project which is found at:

.PP
Notes


.PP
For MPEG-1 encoding a typical (45 minute running time) show or 90 odd
minute movie from an analog broadcast a constant bit-rate of around
1800 kBit/sec should be ideal. The resulting files are around 700M for
45 minutes which fits nicely as a raw XA MODE2 data track on a CD-R.
For pure digital sources (DTV or DVD streams and similar) VCD 1152
works fine.

.PP
\fBNote:\fP If you encode VBR MPEG1 (-q) remember the Hardware was
probably not designed to do the playback because it is not in the
specifications. If it works be very happy. I've noticed that it helps
when you have an MPEG1 Stream to tell vcdimager that it is an SVCD.
vcdimager complains (but only with a warning and not a fatal error) but
you should be able to burn it. This could convince the player to use
different routines in its firmware and play it back correct, but there is 
no guarantee of that.

.PP
Storing MPEGs


.PP
If you record the data as XA mode 2 tracks you can fit appreciably
more on a CD (at the expense of error correction/detection). You can
use vcdimager to do this and vcdxrip (part of the vcdimager package)
to extract (\(rqrip\(rq) the resulting files. For better Quality
there are SVCD and XVCD and DVD.

.PP
Currently SVCD is fully supported with a pre-set format in mplex
and tools to create disks. MPEG streams that can be played by DVD
player hardware and software can readily produced using mpeg2enc/mplex

.PP
If your player doesn't support SVCD you may well find it can handle
VCD streams that have much higher than standard bit-rates. Often as
much as 2500kBit/sec is possible. The several brands of DVD players
can also play wilding out of spec SVCD and VCD discs.
With higher bit-rates and good quality source material it is worth
trying mpeg2enc's -h flag which produce a stream that is as sharp as
the limits of the VCD standard permits. 

.PP
However, if your player supports it and you have the patience for the
longer encoding times SVCD is a much better alternative. Using a
more efficient MPEG format SVCD more than doubles VCD's resolution
while typically producing files that are less than twice as big.
.SH Creating SVCD


.PP
Super Video CD (SVCD) is an enhan