PECompact Documentation

CODEC Plug-ins

PECompact2 is unique in its genre in that it allows for introduction of third-party CODECs (encoding/decoding algorithms) AND use of any number of CODECs on a single module (file). For example, one could use the LZMA CODEC and the CRC CODEC to 1.) Compress the data and 2.) Perform a CRC check on the data, respectively. Or, one could use an encryption algorithm after a compression algorithm. Or, one could apply compression, encryption, and a message box CODEC that simply displays a message to the user during decoding.

When extremely fast decompression is desired as well as a good compression ratio, we recommend FFCE. It doesn't compress quite as tight as LZMA, but decompresses much more rapidly. FFCE is the default for executables under 48Kb.

PECompact2 includes several CODECs for compression, encryption, and general utility. Some are made available only in the retail (registered) version of PECompact2.

Which CODECs are available for PECompact?
How do I sequence multiple CODECs?
How do I know which CODEC I should use?

Available CODECs:

Name	Filename	Author	Type	Description
aPLib	pec2codec_aplib.dll	Jørgen Ibsen	Compression aPLib	aPLib is a high performance compression algorithm with less decompression overhead than FFCE, but slower and does not compress larger files as well as FFCE. Its decompression code is slightly larger than FFCE's.
BriefLZ	pec2codec_brieflz.dll	Jørgen Ibsen	Compression BriefLZ	BriefLZ is a compression algorithm optimized for fast compression and reasonable ratios.
CRC32	pec2codec_crc32.dll	Jørgen Ibsen	Integrity check CRC32	A simple CRC32 check routine. If the data is found to be corrupt at runtime, you will see a message box stating such and the module will exit.
FFCE *recommended for small files and when faster decompression is desired.	pec2codec_ffce.dll	Jørgen Ibsen	Compression. FFCE	FFCE is the default CODEC for small files. It is a high-performance general purpose compression algorithm. It performs best on larger files and has a decompressor that is slightly smaller than aPLib's
JCALG1	pec2codec_jcalg1.dll	Jeremy Collake	Compression JCALG1	JCALG1 is a high-performance general purpose compression algorithm. Compression is much slower, but (especially) at higher compression levels JCALG1 may perform better than other CODECs on some files.
LZMA *recommended for mid-size to large files, but doesn't decompress as fast as FFCE.	pec2codec_lzma.dll (v1) or pec2codec_lzma2.dll (v2)	LZMA Author: 7-Zip (Igor Pavlov) Codec Author: Jørgen Ibsen / Jeremy Collake	Compression LZMA	LZMA is the default CODEC for mid-size and large-size modules. It is a high performance compression algorithm that generally compresses substantially tighter than any other of the algorithms listed here. Version 1 of the codec (pec2codec_lzma.dll) is faster to compress, but usually doesn't compress as well as version 2 (pec2codec_lzma2.dll). In some cases, version 1 may still compress better than version 2, though this is not common.
MessageBox	pec2codec_messagebox.dll	Jørgen Ibsen	User I/O MessageBox Prompt	At runtime displays a message box entirely configured by the user (at time of encode) and takes action appropriate to the user's response at runtime. For example, one could install a 'Are you sure you want to allow this to run?' Yes/No message box on a script interpetor.
Password	pec2codec_password.dll	Jørgen Ibsen	Encryption Password key TEA	Encrypts a file using password entered by user as key. At runtime, the user is prompted for a password. If correct, the module is decompressed and run. If incorrect, the module exits. TEA encryption is used: http://www.simonshepherd.supanet.com/tea.htm .

CODEC Ordering / Sequence:

The ordering use of CODECs is very important since it dramatically affects the output. For instance, you should always compression before encrypt, else the compression is likely to suffer a terrible penalty since the data was transformed into a much more random state by the encryption. The ordering of CODECs is as specified during compression and reversed during decompression. This means that the following configuration would perform a CRC check on the compressed data, there-by performing in at run-time before decompression:

pec2codec_ffce
pec2codec_crc32

Another example is the case of a password protected and compressed executable with crc32 validation, which should be in a similar order as follows:

pec2codec_ffce
pec2codec_password
pec2codec_crc32

Sometimes you may want to use a single CODEC multiple times, for instance:

pec2codec_crc32
pec2codec_ffce
pec2codec_crc32

This would perform a CRC32 check before and after decompression, making sure that the data supplied to the decompressor is unchanged and that your data is in its exact original state after decompression. Note that this will slightly slow load time, though perhaps not noticably, depending on the size of the data set(s). Typically speaking, such a configuration is redundant.

Since PECompact performs its own quick checksum, it is generally better to not use the CRC32 plug-in unless you really need good image validation.

Which CODEC should I use?

Selecting the appropriate CODEC depends on the size and contents module you are compressing. Often, PECompact can best optimize small files when aPLib, FFCE, or JCALG1 are used with their small decoders. Larger files are typically compressed better by LZMA. Since the additional size of the fast decoder is insignificant for larger files, it is recommended that the fast decoder be used in such cases. For smaller files, the small decoder often performs as well, or better, than the fast decoder.

You should experiment with various CODECs to determine which is appropriate for your application. Some algorithms may perform particularly well on specific data, but generally speaking, FFCE and LZMA are the two typically used.