--where MSE is the mean squared error.
--
--
--One way pamtogif is not backward compatible with ppmtogif is that to specify a transparency (alpha) mask with ppmtogif, you supply the transparency as a separate pseudo-PGM image and use the -diff -urNp a/userguide/ppmtompeg.html b/userguide/ppmtompeg.html ---- a/userguide/ppmtompeg.html 2021-06-02 12:56:59.580286388 +0200 -+++ b/userguide/ppmtompeg.html 1970-01-01 01:00:00.000000000 +0100 -@@ -1,1294 +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 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. -- -- --
pamhomography - map one arbitrary quadrilateral image region to another
-+pamhomography - map one arbitrary quadrilateral image region to another - - -