+-where MSE is the mean squared error.
+-
+-
+-pamstereogram pays no attention the the image's tuple ++
pamstereogram pays no attention the image's tuple + type and ignores all planes other than plane 0.
+ +Like any Netpbm program, pamstereogram will accept PNM +diff --git a/userguide/pamtofits.html b/userguide/pamtofits.html +index 445b326..0ecc806 100644 +--- a/userguide/pamtofits.html ++++ b/userguide/pamtofits.html +@@ -54,7 +54,7 @@ approximation. +
The FITS specification does not specify which data in the file corresponds +-to which pixel in the image (i.e. which bytes are the the top left pixel, ++to which pixel in the image (i.e. which bytes are the top left pixel, + etc.). Netpbm uses the common sense, most popular arrangement: row major, top + to bottom, left to right. That means in a 10 wide by 20 high image, the first + 10 pixels in the file are the top row and the last 10 are the bottom row. +diff --git a/userguide/pamtojpeg2k.html b/userguide/pamtojpeg2k.html +index 06b6113..046d740 100644 +--- a/userguide/pamtojpeg2k.html ++++ b/userguide/pamtojpeg2k.html +@@ -181,7 +181,7 @@ its goal is similar to JPEG. It has two main differences from JPEG. +
One difference is that it does a much better job on most images of + throwing out information in order to achieve a smaller output. That + means when you reconstruct the image from the resulting compressed +-file, it looks a lot closer to the image you started with with ++file, it looks a lot closer to the image you started with + JPEG-2000 than with JPEG, for the same compressed file size. Or, looked + at another way, with JPEG-2000 you get a much smaller file than with + JPEG for the same image quality. +diff --git a/userguide/pamtotiff.html b/userguide/pamtotiff.html +index f07d227..c7a48a0 100644 +--- a/userguide/pamtotiff.html ++++ b/userguide/pamtotiff.html +@@ -124,7 +124,7 @@ format it produces are therefore controlled by that library. +
By default, pamtotiff creates a TIFF file with no + compression. This is your best bet most of the time. If you want to + try another compression scheme or tweak some of the other even more +-obscure output options, there are a number of options which which to ++obscure output options, there are a number of options which to + play. + +
Before Netpbm 8.4 (April 2000), the default was to use LZW compression. +diff --git a/userguide/pamtouil.html b/userguide/pamtouil.html +index 1074119..6c2356b 100644 +--- a/userguide/pamtouil.html ++++ b/userguide/pamtouil.html +@@ -57,7 +57,7 @@ in the RGB database. + +
All characters referred to herein are encoded in ASCII. +-"newline" refers the the character known in ASCII as Line ++"newline" refers the character known in ASCII as Line + Feed or LF. A "white space" character is space, CR, LF, + TAB, VT, or FF (I.e. what the ANSI standard C isspace() function + calls white space). +diff --git a/userguide/pbmtolj.html b/userguide/pbmtolj.html +index ce7e9bb..6da4555 100644 +--- a/userguide/pbmtolj.html ++++ b/userguide/pbmtolj.html +@@ -83,7 +83,7 @@ and end of the output file. + +
All characters referred to herein are encoded in ASCII. +-"newline" refers the the character known in ASCII as Line ++"newline" refers the character known in ASCII as Line + Feed or LF. A "white space" character is space, CR, LF, + TAB, VT, or FF (I.e. what the ANSI standard C isspace() function + calls white space). +diff --git a/userguide/pngtopam.html b/userguide/pngtopam.html +index 8185843..09406ef 100644 +--- a/userguide/pngtopam.html ++++ b/userguide/pngtopam.html +@@ -269,7 +269,7 @@ change to the package in Netpbm's renaissance. It and pnmtopng + were simply copied from the + pnmtopng package by Greg Roelofs. Those were based on +-simpler reference applications by by Alexander Lehmann ++simpler reference applications by Alexander Lehmann + <alex@hal.rhein-main.de> and Willem van Schaik + <willem@schaik.com> and distributed with their PNG library. + +diff --git a/userguide/pnmnorm.html b/userguide/pnmnorm.html +index c4d2558..5d3ca49 100644 +--- a/userguide/pnmnorm.html ++++ b/userguide/pnmnorm.html +@@ -146,7 +146,7 @@ value 99 or the white value 101. + option. Sometimes, too much contrast is a bad thing. If your + intensities are all concentrated in the middle, -bpercent=2 and + -wpercent=1 might mean that an intensity of 60 gets stretched +-up to 100 and and intensity of 20 gets stretched down to zero, for a ++up to 100 and intensity of 20 gets stretched down to zero, for a + range expansion of 150% (from a range of 40 to a range of 100). That + much stretching means two adjacent pixels that used to differ in + intensity by 4 units now differ by 10, and that might be unsightly. +diff --git a/userguide/pnmtopalm.html b/userguide/pnmtopalm.html +index 94aa6ff..9ca9c0d 100644 +--- a/userguide/pnmtopalm.html ++++ b/userguide/pnmtopalm.html +@@ -164,7 +164,7 @@ the -colormap option, for much the same reason. + +
All characters referred to herein are encoded in ASCII. +-"newline" refers the the character known in ASCII as Line ++"newline" refers the character known in ASCII as Line + Feed or LF. A "white space" character is space, CR, LF, + TAB, VT, or FF (I.e. what the ANSI standard C isspace() function + calls white space). +diff --git a/userguide/ppmtopj.html b/userguide/ppmtopj.html +index c07c1d9..b50be28 100644 +--- a/userguide/ppmtopj.html ++++ b/userguide/ppmtopj.html +@@ -61,7 +61,7 @@ You could convert your input to this format like this: + pnmremap -map 8color.pam testimg.pam | ppmtopj + + +-Or you could use use ++Or you could use +
+ ppmdither -red 2 -green 2 -blue 2 ++diff --git a/userguide/qrttoppm.html b/userguide/qrttoppm.html +index b6bf976..112bf50 100644 +--- a/userguide/qrttoppm.html ++++ b/userguide/qrttoppm.html +@@ -22,7 +22,7 @@ qrttoppm - convert output from the QRT ray tracer to a PPM image + +
This program is part of Netpbm. + +-
qrttoppm reads a QRT file as input and and produces a PPM ++
qrttoppm reads a QRT file as input and produces a PPM + image as output. + + +diff --git a/userguide/sbigtopgm.html b/userguide/sbigtopgm.html +index 400bcaf..78f9454 100644 +--- a/userguide/sbigtopgm.html ++++ b/userguide/sbigtopgm.html +@@ -22,7 +22,7 @@ sbigtopgm - convert an SBIG CCDOPS file to PGM + +
This program is part of Netpbm. + +-
sbigtopgm reads an an image file in the native format used ++
sbigtopgm reads an image file in the native format used + by the Santa Barbara Instrument Group (SBIG) astronomical CCD cameras, + and produces a PGM image as output. Additional information on SBIG + cameras and documentation of the file format is available at the Web +diff --git a/userguide/srftopam.html b/userguide/srftopam.html +index b27f133..c98586f 100644 +--- a/userguide/srftopam.html ++++ b/userguide/srftopam.html +@@ -30,7 +30,7 @@ + +
This program is part of Netpbm.
+ +-srftopam reads a a SRF image file as input and produces a ++
srftopam reads a SRF image file as input and produces a + multi-image stream of PAM images as output. + +
This program performs the inverse of the conversion that pamtosrf +diff --git a/userguide/sunicontopnm.html b/userguide/sunicontopnm.html +index 6ccbcde..0290f7b 100644 +--- a/userguide/sunicontopnm.html ++++ b/userguide/sunicontopnm.html +@@ -54,7 +54,7 @@ mostly XPM files. + xbmtoppm, + infotopam, + pbm +-pbm ++pgm + +
xpmtoppm can't handle a line longer than 8K characters in +-the the XPM input. If an input line exceeds this limit, ++the XPM input. If an input line exceeds this limit, + xpmtoppm quits with an error message to that effect. Before + Netpbm 10.30 (October 2005), the limit was 2K. + +diff --git a/userguide/infotopam.html b/userguide/infotopam.html +index 9818c59..177f4d4 100644 +--- a/userguide/infotopam.html ++++ b/userguide/infotopam.html +@@ -110,7 +110,7 @@ using the -forcecolor option.
+To override the colors, first specify how many colors to override using + -numcolors, then specify an (index color) pair for each color + you want to override, where index is a value from 0 to 3 and +- color the the new color for that index. Specify color as ++ color the new color for that index. Specify color as + described for the ppm_parsecolor() + argument.
Because the transformation is not linear, you need a greater maxval + in the output in order not to lose any information from the input. +-For example, if you convert to radiance-linear sample values with with ++For example, if you convert to radiance-linear sample values with + -ungamma -bt709ramp and default gamma value, and your maxval is + 255 on both input and output, 3 different input sample values all + generate output sample value 254. In order to have a different output +diff --git a/userguide/ppmtompeg.html b/userguide/ppmtompeg.html +deleted file mode 100644 +index 4fa4a53..0000000 +--- a/userguide/ppmtompeg.html ++++ /dev/null +@@ -1,1291 +0,0 @@ +- +- +-
+-This program is part of Netpbm. +- +-
ppmtompeg produces an MPEG-1 video stream. MPEG-1 is the +-first great video compression method, and is what is used in Video CDs +-(VCD). ppmtompeg originated in the year 1995. DVD uses a more +-advanced method, MPEG-2. There is an even newer method called MPEG-4 +-which is also called Divx. I don't know where one finds that used. +- +-
There's technically a difference between a compression method for +-video and an actual file (stream) format for a movie, and I don't know +-if it can be validly said that the format of the stream +-ppmtompeg produces is MPEG-1. +- +-
Mencoder from the Mplayer +-package is probably superior for most video format generation +-needs, if for no other reason than that it is more popular. +- +-
The programming library PM2V +-generates MPEG-2 streams. +- +-
Use Mplayer (not part of Netpbm) +-to do the reverse conversion: to create a series of PNM files from an MPEG +-stream. +- +-
param_file is a parameter file which includes a list of +-input files and other parameters. The file is described in detail +-below. +- +-
To understand this program, you need to understand something about +-the complex MPEG-1 format. One source of information about this +-standard format is the section Introduction to MPEG in the Compression FAQ. +- +-
The -gop, -combine_gops, -frames, and +--combine_frames options are all mutually exclusive. +- +-
These statistics include how many I, P, and B frames there were, +-and information about compression and quality. +- +- +-
Thus, unless you're mixing and matching GOP files from different +-sources, you can simply use the same parameter file for creating the +-GOP files (-gop) and for later turning them into an MPEG stream +-(-combine_gops). +- +- +-
Use ppmtompeg -combine_frames to combine these frames later into +-an MPEG stream. +- +- +-
The parameter file may specify input frame files in the same manner +-as normal input files -- except instead of using INPUT_DIR, INPUT, and +-END_INPUT, use FRAME_INPUT_DIR, FRAME_INPUT, and FRAME_END_INPUT. If +-no input frame files are specified, then the default is to use the +-output file name with suffix .frame.frame_num, with +-frame_num starting from 0, as the input files. +- +- +- +-
The output is in the form of a matrix, each entry corresponding to one +-motion vector in the search window. The center of the matrix +-represents (0,0) motion vectors. +- +-
The parameter file must contain the following +-lines (except when using the -combine_gops or -combine_frames +-options): +- +-
+- PATTERN IBBPBBPBBPBBPBB +-+- +-
See I Frames, P Frames, B Frames. +- +-
To have ppmtompeg read all the frames serially from Standard +-Input, specify +-
+- INPUT_DIR stdin +-+- +-
There are three types of lines between INPUT and END_INPUT. First, +-a line may simply be the name of an input file. Second, the line +-may be of the form single_star_expr +-[x-y]. +-single_star_expr can have a single * in it. It is +-replaced by all the numbers between x and y inclusive. So, for +-example, the line tennis*.ppm [12-15] refers to the files +-tennis12.ppm, tennis13.ppm, tennis14.ppm, tennis15.ppm. +- +-
Uniform zero-padding occurs, as well. For example, the line +-football.*.ppm [001-130] refers to the files football.001.ppm, +-football.002.ppm, ..., football.009.ppm, football.010.ppm, ..., +-football.130.ppm. +- +-
The third type of line is: single_star_expr +-[x-y+s], where the +-line is treated exactly as above, except that we skip by s. Thus, the +-line football.*.ppm [001-130+4] refers to the files +-football.001.ppm, football.005.ppm, football.009.ppm, +-football.013.ppm, etc. +- +-
Furthermore, a line may specify a shell command to execute to +-generate lines to be interpreted as described above, as if those lines +-were in the parameter file instead. Use back ticks, like in the +-Bourne Shell, like this: +- +-
+- `cat myfilelist` +-+- +-
+-If input is from Standard Input (per the INPUT_DIR statement), +-ppmtompeg ignores the INPUT/END_INPUT block, but +-it still must be present. +- +-
+- INPUT_CONVERT * +-+- +-
Otherwise, conversion_command is a shell command that causes +-an image in the format your specified with BASE_FILE_FORMAT to +-be written to Standard Output. ppmtompeg executes the command +-once for each line between INPUT and END_INPUT (which is +-normally, but not necessarily, a file name). In the conversion +-command, ppmtompeg replaces each '*' with the contents of that +-line. +- +- If you had a bunch of gif files, you might say: +-
+- INPUT_CONVERT giftopnm * +-+- +- If you have a bunch of separate a.Y, a.U, and a.V files (where +- the U and V have already been subsampled), then you might say: +- +-
+- INPUT_CONVERT cat *.Y *.U *.V +-+- +-
Input conversion is not allowed with input from stdin, so use +- +-
+- INPUT_CONVERT * +-+- +-as described above. +- +-
width and height are the width and height of each +-frame in pixels. +- +-
When ppmtompeg can get this information from the input image +-files, it ignores the SIZE parameter and you may omit it. +- +-
When the image files are in YUV format, the files don't contain +-dimension information, so SIZE is required. +- +-
When ppmtompeg is running in parallel mode, not all of the +-processes in the network have access to the image files, so +-SIZE is required and must give the same dimensions as the +-input image files. +- +-
Normally, it makes sense to make your GOP size a multiple of your +-pattern length (the latter is determined by the PATTERN parameter file +-statement). +- +-
See Group Of Pictures. +- +-
| Reference | +-Compression | +-Speed | +-Quality I | +-Quality P | +-Quality B | +-
|---|---|---|---|---|---|
| Decoded | +-1000 | +-1000 | +-1000 | +-969 | +-919 | +-
| Original | +-885 | +-1373 | +-1000 | +-912 | +-884 | +-
The following lines are optional: +- +-
Before Netpbm 10.26 (January 2005), ppmtompeg would drop +-trailing B frames from your movie, since a movie can't end with a B +-frame. (See I Frames, P Frames, B Frames. +-You would have to specify FORCE_ENCODE_LAST_FRAME to stop +-that from happening and get the same function that ppmtompeg +-has today. +- +- +-
+-The 8 lines immediately following NIQTABLE specify the quantization +-table. Each line defines a table row and consists of 8 integers, +-whitespace-delimited, which define the table columns. +- +-
ratio must be 1.0, 0.6735, 0.7031, 0.7615, 0.8055, 0.8437, +-0.8935, 0.9157, 0.9815, 1.0255, 1.0695, 1.0950, 1.1575, or 1.2015. +- +-
rate must be 23.976, 24, 25, 29.97, 30, 50, 59.94, or 60. +- +-
rate must be an integer. +- +-
A Video Verifying Buffer is a buffer in which a decoder keeps the +-decoded bits in order to match the uneven speed of the decoding with +-the required constant playback speed. +- +-
As ppmtompeg encodes the image, it simulates the decoding +-process in terms of how many bits would be in the VBV as each frame gets +-decoded, assuming a VBV of the size you indicate. +- +-
If you specify the WARN_VBV_UNDERFLOW statement, +-ppmtompeg issues a warning each time the simulation underflows +-the buffer, which suggests that an underflow would occur on playback, +-which suggests the buffer is too small. +- +-
If you specify the WARN_VBV_OVERFLOW statement, +-ppmtompeg issues a warning each time the simulation overflows +-the buffer, which suggests that an overflow would occur on playback, +-which suggests the buffer is too small. +- +-
These options were new in Netpbm 10.26 (January 2005). Before that, +-ppmtompeg issued the warnings always. +- +-
If you specify FORCE_I_ALIGN, ppmtompeg will increase +-the test frames value enough to maintain the alignment. +- +-
If there aren't enough frames for every slave to have the indicated +-number of test frames, ppmtompeg will give some slaves fewer. +- +- +-
Smaller values of t increase communication, but improve load +-balancing. The default is 30 seconds. +- +-
You may specify only one of PARALLEL_TIME_CHUNKS, PARALLEL_CHUNK_TAPER, +-and PARALLEL_PERFECT. PARALLEL_CHUNK_TAPER is usually best. +- +-
You may specify only one of PARALLEL_TIME_CHUNKS, PARALLEL_CHUNK_TAPER, +-and PARALLEL_PERFECT. PARALLEL_CHUNK_TAPER is usually best. +- +- +-
This has the advantage of minimal scheduling overhead. Where slaves +-have different speeds, though, it makes inefficient use of the fast +-ones. Where slaves are the same speed, it also has the disadvantage +-that they all finish at the same time and feed their output to the +-single Combine Server in a burst, which makes less efficient use of +-the Combine Server and thus can increase the total elapsed time. +- +-
You may specify only one of PARALLEL_TIME_CHUNKS, PARALLEL_CHUNK_TAPER, +-and PARALLEL_PERFECT. PARALLEL_CHUNK_TAPER is usually best. +- +-
Be sure to set up .rhosts files or SSH key authorizations +-where needed. Otherwise, you'll have to type in passwords. +- +-
On some HP machines, rsh is the restricted shell, and you want +-to specify remsh. +- +-
This document used to say there was an argument to +-FORCE_I_ALIGN which was the number of frames ppmtompeg +-would use (and was required to be a multiple of the pattern length). +-But ppmtompeg has apparently always ignored that argument, and +-it does now. +- +-
This is mostly useful for debugging. +- +-
This works only if you're using a shared filesystem to communicate +-between the servers. +- +-
This option was new in Netpbm 10.26 (January 2005). +- +-
If you use the -combine_gops option, then you need to specify +-only the SIZE and OUTPUT values in the parameter file. In +-addition, the parameter file may specify input GOP files in the same +-manner as normal input files -- except instead of using INPUT_DIR, +-INPUT, and END_INPUT, use GOP_INPUT_DIR, GOP_INPUT, and GOP_END_INPUT. +-If you specify no input GOP files, then ppmtompeg uses by default the +-output file name with suffix .gop.gop_num, with gop_num +-starting from 0, as the input files. +- +-
If you use the -combine_frames option, then you need to +-specify only the SIZE, GOP_SIZE, and OUTPUT values in the +-parameter file. In addition, the parameter file may specify input +-frame files in the same manner as normal input files -- except instead +-of using INPUT_DIR, INPUT, and END_INPUT, use FRAME_INPUT_DIR, +-FRAME_INPUT, and FRAME_END_INPUT. If no input frame files are +-specified, then the default is to use the output file name with suffix +-.frame.frame_num, with frame_num starting from 0, +-as the input files. +- +-
Any number of spaces and tabs may come between each option and value. Lines +-beginning with # are ignored. Any other lines are ignored except for +-those between INPUT and END_INPUT. This allows you to use the same +-parameter file for normal usage and for -combine_gops and +--combine_frames. +- +-
The file format is case-sensitive so all keywords should be in +-upper case. +- +-
The statements may appear in any order, except that the order within +-a block statement (such as INPUT ... END INPUT) is significant. +- +-
ppmtompeg is prepared to handle up to 16 B frames between +-reference frames when encoding with input from stdin. (To build a +-modified ppmtompeg with a higher limit, change the constant +-B_FRAME_RUN in frame.c and recompile). +- +-
The quantization scale values (qscale) give a trade-off between +-quality and compression. Using different Qscale values has very little +-effect on speed. The qscale values can be set separately for I, P, and +-B frames. +- +-
You select the qscale values with the IQSCALE, +-PQSCALE, and BSCALE parameter file statements. +- +-
A qscale value is an integer from 1 to 31. Larger numbers give
+-better compression, but worse quality. In the following, the quality
+-numbers are peak signal-to-noise ratio, defined as:
+-
+-where MSE is the mean squared error.
+-
+-
+-
Flower garden tests: +- +-
| Qscale | +-I Frames | +-P Frames | +-B Frames | +-
|---|---|---|---|
| 1 | +-43.2 | +-46.3 | +-46.5 | +-
| 6 | +-32.6 | +-34.6 | +-34.3 | +-
| 11 | +-28.6 | +-29.5 | +-30.0 | +-
| 16 | +-26.3 | +-26.8 | +-28.6 | +-
| 21 | +-24.7 | +-25.0 | +-27.9 | +-
| 26 | +-23.5 | +-23.9 | +-27.5 | +-
| 31 | +-22.6 | +-23.0 | +-27.3 | +-
| Qscale | +-I Frames | +-P Frames | +-B Frames | +-
|---|---|---|---|
| 1 | +-2 | +-2 | +-2 | +-
| 6 | +-7 | +-10 | +-15 | +-
| 11 | +-11 | +-18 | +-43 | +-
| 16 | +-15 | +-29 | +-97 | +-
| 21 | +-19 | +-41 | +-173 | +-
| 26 | +-24 | +-56 | +-256 | +-
| 31 | +-28 | +-73 | +-330 | +-
There are several different motion vector search techniques +-available. There are different techniques available for P frame +-search and B frame search. Using different search techniques present +-little difference in quality, but a large difference in compression +-and speed. +- +-
There are 4 types of P frame search: Exhaustive, TwoLevel, +-SubSample, and Logarithmic. +- +-
There are 3 types of B frame search: Exhaustive, Cross2, and +-Simple. +- +-The recommended search techniques are TwoLevel and Logarithmic for +-P frame search, and Cross2 and Simple for B frame search. Here are +-some numbers comparing the different search methods: +- +-
| Technique | +-Compression1 | +-Speed 2 | +-Quality 3 | +-
|---|---|---|---|
| Exhaustive | +-1000 | +-1000 | +-1000 | +-
| SubSample | +-1008 | +-2456 | +-1000 | +-
| TwoLevel | +-1009 | +-3237 | +-1000 | +-
| Logarithmic | +-1085 | +-8229 | +-998 | +-
| Technique | +-Compression1 | +-Speed2 | +-Quality3 | +-
|---|---|---|---|
| Exhaustive | +-1000 | +-1000 | +-1000 | +-
| Cross2 | +-975 | +-1000 | +-996 | +-
| Simple | +-938 | +-1765 | +-991 | +-
For some reason, Simple seems to give better compression, but it +-depends on the image sequence. +- +-
Select the search techniques with the PSEARCH_ALG and +-BSEARCH_ALG parameter file statements. +- +- +- +-
A Group of Pictures (GOP) is a roughly independently decodable +-sequence of frames. An MPEG video stream is made of one or more +-GOP's. You may specify how many frames should be in each GOP with the +-GOP_SIZE parameter file statement. A GOP always starts with an +-I frame. +- +-
Instead of encoding an entire sequence, you can encode a single +-GOP. To do this, use the -gop command option. You can later +-join the resulting GOP files at any time by running ppmtompeg +-with the -combine_gops command option. +- +- +-
A slice is an independently decodable unit in a frame. It can be +-as small as one macroblock, or it can be as big as the entire frame. +-Barring transmission error, adding slices does not change quality or +-speed; the only effect is slightly worse compression. More slices are +-used for noisy transmission so that errors are more recoverable. Since +-usually errors are not such a problem, we usually just use one slice +-per frame. +- +-
Control the slice size with the SLICES_PER_FRAME parameter +-file statement. +- +-
Some MPEG playback systems require that each slice consist of whole +-rows of macroblocks. If you are encoding for this kind of player, if +-the height of the image is H pixels, then you should set the +-SLICES_PER_FRAME to some number which divides H/16. For example, if +-the image is 240 pixels (15 macroblocks) high, then you should use +-only 15, 5, 3, or 1 slices per frame. +- +-
Note: these MPEG playback systems are really wrong, since the MPEG +-standard says this doesn't have to be so. +- +- +- +-
The search window is the window in which ppmtompeg searches +-for motion vectors. The window is a square. You can specify the size +-of the square, and whether to allow half-pixel motion vectors or not, +-with the RANGE and PIXEL parameter file statements. +- +-
In MPEG-1, a movie is represented as a sequence of MPEG frames, +-each of which is an I Frame, a P Frame, or a B Frame. Each represents +-an actual frame of the movie (don't get confused by the dual use of +-the word "frame." A movie frame is a graphical image. An MPEG frame +-is a set of data that describes a movie frame). +- +-
An I frame ("intra" frame) describes a movie frame in isolation -- +-without respect to any other frame in the movie. A P frame +-("predictive" frame) describes a movie frame by describing how it +-differs from the movie frame described by the latest preceding I or +-P frame. A B frame ("bidirectional" frame) describes a movie frame by +-describing how it differs from the the movie frames described by the +-nearest I or P frame before and after it. +- +-
Note that the first frame of a movie must be described by an I +-frame (because there is no previous movie frame) and the last movie +-frame must be described by an I or P frame (because there is no +-subsequent movie frame). +- +-
Beyond that, you can choose which frames are represented by which +-types. You specify a pattern, such as IBPBP and ppmtompeg +-simply repeats it over and over throughout the movie. The pattern +-affects speed, quality, and stream size. Here is a chart which shows +-some of the trade-offs: +- +-
| Frame Type | +-Size | +-Speed | +-Quality | +-
|---|---|---|---|
| I frames | +-1000 | +-1000 | +-1000 | +-
| P frames | +-409 | +-609 | +-969 | +-
| B frames | +-72 | +-260 | +-919 | +-
A standard sequence is IBBPBBPBBPBBPBB. +- +-
Select the sequence with the PATTERN parameter file statement. +- +-
Since the last MPEG frame cannot be a B frame (see above), if the +-pattern you specify indicates a B frame for the last movie frame of +-the movie, ppmtompeg makes it an I frame instead. +- +-
Before Netpbm 10.26 (January 2005), ppmtompeg instead drops +-the trailing B frames by default, and you need the +-FORCE_ENCODE_LAST_FRAME parameter file statement to make it do +-this. +- +-
The MPEG frames don't appear in the MPEG-1 stream in the same order that +-the corresponding movie frames appear in the movie -- the B frames come after +-the I and P frames on which they are based. For example, if the movie is +-4 frames that you will represent with the pattern IBBP, the MPEG-1 stream +-will start with an I frame describing movie frame 0. The next frame in +-the MPEG-1 stream is a P frame describing movie frame 3. The last two +-frames in the MPEG-1 stream are B frames describing movie frames 1 and 2, +-respectively. +- +- +-
Specify the input frame images with the INPUT_DIR, +-INPUT, END_INPUT, BASE_FILE_FORMAT, +-SIZE, YUV_FORMAT and INPUT_CONVERT parameter +-file statements. +- +-
Specify the output file with the OUTPUT parameter file statement. +- +- +-
ppmtompeg can generate a variety of statistics about the +-encoding. See the -stat, -snr, -mv_histogram, +--quiet, -no_frame_summary, and -bit_rate_info +-options. +- +- +-
You can run ppmtompeg on multiple machines at once, encoding +-the same MPEG stream. When you do, the machines are used as shown in +-the following diagram. We call this "parallel mode." +- +-
+-
+-
To do parallel processing, put the statement +- +-
+- PARALLEL +-+- +-in the parameter file, followed by a listing of the machines, one +-machine per line, then +- +-
+- END_PARALLEL +-+- +-Each of the machine lines must be in one of two forms. If the machine +-has filesystem access to the input files, then the line is: +- +-
+-machine user executable +- +-
The executable is normally ppmtompeg (you may need to give +-the complete path if you've built for different architectures). If +-the machine does not have filesystem access to the input files, the line +-is: +- +-
REMOTE machine user executable +-parameter file +- +-
The -max_machines command option limits the number of +-machines ppmtompeg will use. If you specify more machines in +-the parameter file than -max_machines allows, ppmtompeg +-uses only the machines listed first. This is handy if you want to +-experiment with different amounts of parallelism. +- +-
In general, you should use full path file names when describing +-executables and parameter files. This includes the parameter +-file argument on the original invocation of ppmtompeg. +- +-
All file names must be the same on all systems (so if e.g. you're +-using an NFS filesystem, you must make sure it is mounted at the same +-mountpoint on all systems). +- +-
Because not all of the processes involved in parallel operation +-have easy access to the input files, you must specify the SIZE +-parameter file statement when you do parallel operation. +- +-
The machine on which you originally invoke ppmtompeg is the +-master machine. It hosts a "combine server,", a +-"decode server," and a number of "i/o servers," +-all as separate processes. The other machines in the network (listed +-in the parameter file) are slave machines. Each hosts a single +-process that continuously requests work from the master and does it. +-The slave process does the computation to encode MPEG frames. It +-processes frames in batches identified by the master. +- +-
The master uses a remote shell command to start a process on a +-slave machine. By default, it uses an rsh shell command to do +-this. But use the RSH parameter file statement to control +-this. The shell command the master executes remotely is +-ppmtompeg, but with options to indicate that it is to perform +-slave functions. +- +-
The various machines talk to each other over TCP connections. Each +-machine finds and binds to a free TCP port number and tells its +-partners the port number. These port numbers are at least 2048. +- +-
Use the PARALLEL_TEST_FRAMES, PARALLEL_TIME_CHUNKS, and +-PARALLEL_PERFECT parameter file statements to control the way the +-master divides up work among the slaves. +- +-
Use the -nice command option to cause all slave processes to run +-"nicely," i.e. as low priority processes. That way, this substantial and +-long-running CPU load will have minimal impact on other, possibly +-interactive, users of the systems. +- +- +-
Here is a look at ppmtompeg speed, in single-node (not parallel) +-operation: +- +-
| Machine Type | +-Macroblocks per second1 | +-
|---|---|
| HP 9000/755 | +-280 | +-
| DEC 3000/400 | +-247 | +-
| HP 9000/750 | +-191 | +-
| Sparc 10 | +-104 | +-
| DEC 5000 | +-68 | +-
The measurements in the table are with inputs and outputs via a +-conventional locally attached filesystem. If you are using a network +-filesystem over a single 10 MB/s Ethernet, that constrains your speed more +-than your CPU speed. In that case, don't expect to get better than 4 +-or 5 frames per second no matter how fast your CPUs are. +- +-
Network speed is even more of a bottleneck when the slaves do not +-have filesystem access to the input files -- i.e. you declare them +-REMOTE. +- +-
Where I/O is the bottleneck, size of the input frames can make a big +-difference. So YUV input is better than PPM, and JPEG is better than +-both. +- +-
When you're first trying to get parallel mode working, be sure to +-use the -debug_machines option so you can see what's going on. +-Also, -debug_sockets can help you diagnose communication +-problems. +- +- +-