# PPMTOMPEG

Updated: 14 July 2001
Index

## NAME

ppmtompeg - encode an MPEG-1 bitstream

## SYNOPSIS

ppmtompeg [options] parameter-file

## DESCRIPTION

ppmtompeg produces an MPEG-1 video 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 Introduction to MPEG.

## OPTIONS

The -gop, -combine_gops, -frames, and -combine_frames options are all exclusive.

-stat stat_file
  This option causes ppmtompeg to append the statistics that it write to Standard Output to the file stat_file as well. The statistics use the following abbreviations: bits per block (bpb), bits per frame (bpf), seconds per frame (spf), and bits per second (bps).

  These statistics include how many I, P, and B frames there were, and information about compression and quality.

-quiet num_seconds
  causes ppmtompeg not to report remaining time more often than every num_seconds seconds (unless the time estimate rises, which will happen near the beginning of the run). A negative value tells ppmtompeg not to report at all. 0 is the default (reports once after each frame). Note that the time remaining is an estimate and does not take into account time to read in frames.
-realquiet
  causes ppmtompeg to run silently, with the only screen output being errors. Particularly useful when reading input from stdin.
-no_frame_summary
  This option prevents ppmtompeg from printing a summary line for each frame
-float_dct
  forces ppmtompeg to use a more accurate, yet more computationally expensive version of the DCT.
-gop gop_num
  causes ppmtompeg to encode only the numbered GOP (first GOP is 0). The parameter file is the same as for normal usage. The output file will be the normal output file with the suffix .gop.gop_num. ppmtompeg does not output any sequence information.
-combine_gops
  causes ppmtompeg simply to combine some GOP files into a single MPEG output stream. ppmtompeg inserts a sequence header and trailer. In this case, the parameter file needs onlly contain the YUV_SIZE value, an output file, and perhaps a list of input GOP files (see below). If you don't supply a list of input GOP files is used, then ppmtompeg assumes you're using the same parameter file you used when you created the input (with the -gop option) and calculates the corresponding gop filenames itself. If this is not the case, you can 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 no input GOP files are specified, then the default is to use the output file name with suffix .gop.gop_num, with gop_num starting from 0, as the input files.

  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).

-frames first_frame last_frame
  This option causes ppmtompeg to encode only the frames numbered first_frame to last_frame, inclusive. The parameter file is the same as for normal usage. The output will be placed in separate files, one per frame, with the file names being the normal output file name with the suffix .frame.frame_num. No GOP header information is output. (Thus, the parameter file need not include the GOP_SIZE value)

  Use ppmtompeg -combine_frames to combine these frames later into an MPEG stream.

-combine_frames
  This option causes ppmtompeg simply to combine some frames into a single MPEG stream. Sequence and GOP headers are inserted appropriately. In this case, the parameter file needs to contain only the YUV_SIZE value, the GOP_SIZE value, an output file, and perhaps a list of frame files (see below).

  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.

-nice
  This option causes ppmtompeg to run any remote processes "nicely," i.e. at low priority. (This is relevant only if you are running ppmtompeg in parallel mode. Otherwise, there are no remote processes). See 'man nice.'
-max_machines num_machines
  This option causes ppmtompeg to use no more than num_machines machines as slaves for use in parallel encoding.
-snr
  This option causes ppmtompeg to include the signal-to-noise ratio in the reported statistics. Prints SNR (Y U V) and peak SNR (Y U V) for each frame. In summary, prints averages of luminance only (Y). SNR is defined as 10*log(variance of original/variance of error). Peak SNR is defined as 20*log(255/RMSE). Note that ppmtompeg runs a little slower when you use this option.
-mse
  This option causes ppmtompeg to report the mean squared error per block. It also automatically reports the quality of the images, so there is no need to specify -snr then.
-bit_rate_info rate_file
  This option makes ppmtompeg write bit rate information into the file rate_file. Bit rate information is bits per frame, and also bits per I-frame-to-I-frame.
-mv_histogram
  This option causes ppmtompeg to print a histogram of the motion vectors as part of statistics. There are three histograms -- one for P frame, one for forward B frame, and one for backward B frame motion vectors.

  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.

## PARAMETER FILE

The parameter file must contain the following lines (except when using the -combine_gops or -combine_frames options):

PATTERN pattern
  This statement specifies the pattern (sequence) of I frames, P frames, and B frames. pattern is just a sequence of the letters I, P, and B with nothing between. Example:

          PATTERN IBBPBBPBBPBBPBB

  See I Frames, P Frames, B Frames.

OUTPUT output file
  This names the file where the output MPEG stream goes.
INPUT_DIR directory
  all input files must reside in this directory. If you want to refer to the current directory, use '.' A null directory refers to the root directory). If input files will be coming in from standard input, use directory=stdin.
INPUT
  This line must be followed by a list of the input files (in display order) and then the line END_INPUT.

  There are three types of lines between INPUT and END_INPUT. First, a line may simply be the name of an input file. Secondly, 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.

BASE_FILE_FORMAT {PPM | PNM | YUV | JPEG | JMOVIE}
  ppmtompeg must convert all input files to one of the following formats as a first step of processing: PNM, YUV, JPEG(v4), or JMOVIE. (The conversion may be trivial if your input files are alrady in one of these formats). This line specifies which of the four formats. PPM is actually a subset of PNM. The separate specification is allowed for backward compatibility. Use PNM instead of PPM in new applications.
INPUT_CONVERT conversion_command
  You must specify how to convert a file to the base file format. If no conversion is necessary, then you would just say:

           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.

YUV_SIZE width x height
  This is meaningful only when BASE_FILE_FORMAT specifies YUV format, and then it is required. The other formats have dimension information contained within the image, but YUV does not so you must tell ppmtompeg the dimensions separately.

  width and height are the width and height of each frame in pixels.

YUV_FORMAT {ABEKAS | PHILLIPS | UCB | EYUV | pattern}
  This is meaningful only when BASE_FILE_FORMAT specifies YUV format, and then it is required. It specifies the sub-format of the YUV class.
GOP_SIZE n
  n is the number of frames in a Group of Pictures. Except that because a GOP must start with an I frame, ppmtompeg makes a GOP as much longer than n as it has to to make the next GOP start with an I frame.

  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.

SLICES_PER_FRAME n
  n is roughly the number of slices per frame. Note, at least one MPEG player may complain if slices do not start at the left side of an image. To ensure this does not happen, make sure the number of rows is divisible by SLICES_PER_FRAME.
PIXEL {FULL | HALF}
  use half-pixel motion vectors, or just full-pixel ones It is usually important that you use half-pixel motion vectors, because it results in both better quality and better compression.
RANGE n
  Use a search range of n pixels in each of the four directions from a subject pixel. (So the search window is a square n*2 pixels on a side).
PSEARCH_ALG {EXHAUSTIVE | TWOLEVEL | SUBSAMPLE | LOGARITHMIC}
  This statement tells ppmtompeg what kind of search technique (algorithm) to use for P frames. You select the desired combination of speed and compression. EXHAUSTIVE gives the best compression, but LOGARITHMIC is the fastest. TWOLEVEL is an exhaustive full-pixel search, followed by a local half- pixel search around the best full-pixel vector (the PIXEL option is ignored for this search technique).
BSEARCH_ALG {SIMPLE | CROSS2 | EXHAUSTIVE}
  This statement tells ppmtompeg what kind of search technique (algorithm) to use for B frames. SIMPLE means find best forward and backward vectors, then interpolate. CROSS2 means find those two vectors, then see what backward vector best matches the best forward vector, and vice versa. EXHAUSTIVE does an n-squared search and is extremely slow in relation to the others (CROSS2 is about half as fast as SIMPLE).
IQSCALE n
  Use n as the qscale for I frames. See Qscale.
PQSCALE n
  Use n as the qscale for P frames. See Qscale.
BQSCALE n
  Use n as the qscale for B frames. See Qscale.
REFERENCE_FRAME {ORIGINAL | DECODED}
  This statement determines whether ppmtompeg uses the original images or the decoded images when computing motion vectors. Using decoded images is more accurate and should increase the playback quality of the output, but it makes the encoding take longer and seems to give worse compression. It also causes some complications with parallel encoding. (see the section on parallel encoding). One thing you can do as a trade-off is select ORIGINAL here, and lower the qscale (see QSCALE if the quality is not good enough.

  Original or Decoded? (Normalized)
  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:

NIQTABLE
  This statement specifies a custom non-intra quantization table. If you don't specify this statement, ppmtompeg uses a default non-intra quantization table.

  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.

IQTABLE
  This is analogous to NIQTABLE, but for the intra quantization table.
ASPECT_RATIO ratio
  This statement specifies the aspect ratio for ppmtompeg to specify in the MPEG output. I'm not sure what this is used for.

  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.

FRAME_RATE rate
  This specifies the frame rate for ppmtompeg to specify in the MPEG output. Some players use this value to determine the playback rate.

  rate must be 23.976, 24, 25, 29.97, 30, 50, 59.94, or 60.

BIT_RATE rate
  This specifies the bit rate for Constant Bit Rate (CBR) encoding.

  rate must be an integer.

BUFFER_SIZE size
  This specifies the value ppmtompeg is to specify in the MPEG output for the Video Buffering Verifier (VBV) buffer size needed to decode the sequence. Some playback systems use this to prevent under/overflow.

The following statements apply only to parallel operation:

PARALLEL
  This statement, paired with END PARALLEL, is what causes ppmtompeg to operate in parallel mode. See Parallel Operation.
END PARALLEL
  This goes with PARALLEL.
PARALLEL_TEST_FRAMES n
  The master starts off by measuring each slave's speed. It does this by giving each slave n frames to encode and noting how long the slave takes to finish. These are not just test frames, though -- they're real frames and the results become part of the output. You should specify at least 3, preferably 5 or 6, to insure a good estimate. The default is 3.
PARALLEL_TIME_CHUNKS t
  When you specify this statement, the master attempts to feed work to the slaves in chunks that take t seconds to process. It uses the speed measurement it made when it started up (see PARALLEL_TEST_FRAMES) to decide how many frames to put in the chunk. This statement obviously doesn't affect the first batch of work sent to each slave, which is the one used to measure the slave's speed.

  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.

PARALLEL_CHUNK_TAPER
  When you specify this statement, the master distributes work like with PARALLEL_TIME_CHUNKS, except that the master chooses the number of seconds for the chunks. It starts with a large number and, as it gets closer to finishing the job, reduces it. That way, it reduces scheduling overhead when precise scheduling isn't helpful, but still prevents a slave from finishing early after all the work has already been handed out to the other slaves, and then sitting idle while there's still work to do.

  You may specify only one of PARALLEL_TIME_CHUNKS, PARALLEL_CHUNK_TAPER, and PARALLEL_PERFECT. PARALLEL_CHUNK_TAPER is usually best.

PARALLEL_PERFECT
  If this statement is present, ppmtompeg schedules on the assumption that each machine is about the same speed. The master will simply divide up the frames evenly between the slaves -- each slave gets the same number of frames. If some slaves are faster than others, they will finish first and remain idle while the slower slaves continue.

  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.

RSH remote_shell_command
  ppmtompeg executes the shell command remote_shell_command to start a process on another machine. The default command is rsh, and whatever command you specify must have compatible semantics. Be sure to set up .rhosts files where needed.

  On some HP machines, rsh is the restricted shell, and you want to specify remsh.

FORCE_I_ALIGN n
  This statement forces each slave to encode a chunk of n frames, where n must be a multiple of the pattern length (see PATTERN). Since the first frame in any pattern is an I frame, this forces each chunk encoded by a slave to begin with an I frame.

### Parameter File Notes

If you use the -combine_gops option, then you need to specify only the YUV_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 YUV_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).

## GENERAL USAGE INFORMATION

### Qscale

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 vs Quality
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 vs Compression
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

### Search Techniques

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:

P frame Motion Vector Search (Normalized)
Technique | Compression1 | Speed 2 | Quality 3
--- | --- | --- | ---
Exhaustive | 1000 | 1000 | 1000
SubSample | 1008 | 2456 | 1000
TwoLevel | 1009 | 3237 | 1000
Logarithmic | 1085 | 8229 | 998

B frame Motion Vector Search (Normalized)
Technique | Compression1 | Speed2 | Quality3
--- | --- | --- | ---
Exhaustive | 1000 | 1000 | 1000
Cross2 | 975 | 1000 | 996
Simple | 938 | 1765 | 991

1Smaller numbers are better compression. 2Larger numbers mean faster execution. 3Larger numbers mean better quality.

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.

### Group Of Pictures (GOP)

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.

### Slices

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.

### Search Window

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.

### I Frames, P Frames, B Frames

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.

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.

Note that a movie must start with an I frame (because there is no previous movie frame) and end with an I or P frame (because there is no subsequent movie frame)

Beyond that, you can choose which frames are of 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 compression. Here is a chart which shows some of the trade-offs:

Comparison of I/P/B Frames (Normalized)
Frame Type | Compression | Speed | Quality
--- | --- | --- | ---
I frames | 1000 | 1000 | 1000
P frames | 409 | 609 | 969
B frames | 72 | 260 | 919

(this is with constant qscale)

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 B frames for the last movie frames, ppmtompeg simply drops the last movie frames from the movie. To insure that every movie frame is represented in the MPEG stream, use the FORCE_ENCODE_LAST_FRAME parameter file statement to force the last frame to be an I frame regardless of the pattern you specify with PATTERN.

### Specifying Input and Output Files

Specify the input frame images with the INPUT_DIR, INPUT, END_INPUT, BASE_FILE_FORMAT, YUV_SIZE, YUV_FORMAT and INPUT_CONVERT parameter file statements.

Specify the output file with the OUTPUT parameter file statement.

### Statistics

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.

## PARALLEL OPERATION

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.

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).

The machine on which you originally invoke ppmtompeg runs the master and I/O server processes, and the other machines (listed in the parameter file) do the computation.

The master generally uses rsh to start a process on a slave machine. But use the RSH parameter file statement to control this.

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.

## SPEED

Here is a look at ppmtompeg speed, in single-node (not parallel) operation:

Compression Speed
Machine Type | Macroblocks per second1
--- | ---
HP 9000/755 | 280
DEC 3000/400 | 247
HP 9000/750 | 191
Sparc 10 | 104
DEC 5000 | 68

1A macroblock is a 16x16 pixel square

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.

## AUTHORS

  Kevin Gong - University of California, Berkeley, keving@cs.berkeley.edu
  Ketan Patel - University of California, Berkeley, kpatel@cs.berkeley.edu
  Dan Wallach - University of California, Berkeley, dwallach@cs.berkeley.edu
  Darryl Brown - University of California, Berkeley, darryl@cs.berkeley.edu
  Eugene Hung - University of California, Berkeley, eyhung@cs.berkeley.edu
  Steve Smoot - University of California, Berkeley, smoot@cs.berkeley.edu

## Index

- NAME
- SYNOPSIS
- DESCRIPTION
- OPTIONS
- PARAMETER FILE
- GENERAL USAGE INFORMATION
- PARALLEL OPERATION
- SPEED
- AUTHORS