From 7bdee4655b3ecdae65429b0cbc6df4a6c4a4e1c1 Mon Sep 17 00:00:00 2001 From: Mathis Rosenhauer Date: Thu, 14 Apr 2016 11:14:57 +0200 Subject: Fix markdown --- README.md | 77 ++++++++++++++++++++++++++++++++------------------------------- 1 file changed, 39 insertions(+), 38 deletions(-) diff --git a/README.md b/README.md index 2791ee4..f5a39e6 100644 --- a/README.md +++ b/README.md @@ -9,22 +9,22 @@ supported, they can also be efficiently coded by grouping exponents and mantissa. Libaec implements -"Golomb-Rice":http://en.wikipedia.org/wiki/Golomb_coding coding as +[Golomb-Rice](http://en.wikipedia.org/wiki/Golomb_coding) coding as defined in the Space Data System Standard documents [121.0-B-2][1] and [120.0-G-2][2]. ## Patents -In [doc/license.txt] a clarification on potentially applying -intellectual property rights is given. +In [license.txt](doc/license.txt) a clarification on potentially +applying intellectual property rights is given. ## Installation -See [INSTALL] for details. +See [INSTALL](INSTALL) for details. ## SZIP Compatibility -[Libaec can replace SZIP][README.SZIP]. +[Libaec can replace SZIP](README.SZIP). ## Encoding @@ -32,8 +32,8 @@ In this context efficiency refers to the size of the encoded data. Performance refers to the time it takes to encode data. Suppose you have an array of 32 bit signed integers you want to -compress. The pointer pointing to the data shall be called *source, -output goes into *dest. +compress. The pointer pointing to the data shall be called `*source`, +output goes into `*dest`. ```C++ #include @@ -82,12 +82,12 @@ output goes into *dest. ... ``` -block_size can vary from 8 to 64 samples. Smaller blocks allow the +`block_size` can vary from 8 to 64 samples. Smaller blocks allow the compression to adapt more rapidly to changing source statistics. Larger blocks create less overhead but can be less efficient if source statistics change across the block. -rsi sets the reference sample interval. A large RSI will improve +`rsi` sets the reference sample interval. A large RSI will improve performance and efficiency. It will also increase memory requirements since internal buffering is based on RSI size. A smaller RSI may be desirable in situations where each RSI will be packetized and possible @@ -95,41 +95,42 @@ error propagation has to be minimized. ### Flags: -* AEC_DATA_SIGNED: input data are signed integers. Specifying this +* `AEC_DATA_SIGNED`: input data are signed integers. Specifying this correctly increases compression efficiency. Default is unsigned. -* AEC_DATA_PREPROCESS: preprocessing input will improve compression +* `AEC_DATA_PREPROCESS`: preprocessing input will improve compression efficiency if data samples are correlated. It will only cost performance for no gain in efficiency if the data is already uncorrelated. -* AEC_DATA_MSB: input data is stored most significant byte first - i.e. big endian. You have to specify AEC_DATA_MSB even if your host +* `AEC_DATA_MSB`: input data is stored most significant byte first + i.e. big endian. You have to specify `AEC_DATA_MSB` even if your host architecture is big endian. Default is little endian on all architectures. -* AEC_DATA_3BYTE: the 17 to 24 bit input data is stored in three +* `AEC_DATA_3BYTE`: the 17 to 24 bit input data is stored in three bytes. This flag has no effect for other sample sizes. -* AEC_RESTRICTED: use a restricted set of code options. This option is - only valid for bits_per_sample <= 4. +* `AEC_RESTRICTED`: use a restricted set of code options. This option is + only valid for `bits_per_sample` <= 4. -* AEC_PAD_RSI: assume that the encoded RSI is padded to the next byte - boundary while decoding. The preprocessor macro ENABLE_RSI_PADDING +* `AEC_PAD_RSI`: assume that the encoded RSI is padded to the next byte + boundary while decoding. The preprocessor macro `ENABLE_RSI_PADDING` needs to be defined while compiling for the encoder to honour this flag. ### Data size: The following rules apply for deducing storage size from sample size -(bits_per_sample): +(`bits_per_sample`): -|_. sample size |_. storage size| -| 1 - 8 bits | 1 byte| -| 9 - 16 bits | 2 bytes| -|17 - 24 bits | 3 bytes (only if AEC_DATA_3BYTE is set)| -|25 - 32 bits | 4 bytes (if AEC_DATA_3BYTE is set)| -|17 - 32 bits | 4 bytes (if AEC_DATA_3BYTE is not set)| + **sample size** | **storage size** +--- | --- + 1 - 8 bits | 1 byte + 9 - 16 bits | 2 bytes +17 - 24 bits | 3 bytes (only if `AEC_DATA_3BYTE` is set) +25 - 32 bits | 4 bytes (if `AEC_DATA_3BYTE` is set) +17 - 32 bits | 4 bytes (if `AEC_DATA_3BYTE` is not set) If a sample requires less bits than the storage size provides, then you have to make sure that unused bits are not set. Libaec does not @@ -138,23 +139,23 @@ if unused bits are set. All input data must be a multiple of the storage size in bytes. Remaining bytes which do not form a complete sample will be ignored. -Libaec accesses next_in and next_out buffers only bytewise. There are -no alignment requirements for these buffers. +Libaec accesses `next_in` and `next_out` buffers only bytewise. There +are no alignment requirements for these buffers. ### Flushing: -aec_encode can be used in a streaming fashion by chunking input and -output and specifying AEC_NO_FLUSH. The function will return if either +`aec_encode` can be used in a streaming fashion by chunking input and +output and specifying `AEC_NO_FLUSH`. The function will return if either the input runs empty or the output buffer is full. The calling -function can check avail_in and avail_out to see what occurred. The -last call to aec_encode() must set AEC_FLUSH to drain all +function can check `avail_in` and `avail_out` to see what occurred. The +last call to `aec_encode()` must set `AEC_FLUSH` to drain all output. aec.c is an example of streaming usage of encoding and decoding. ### Output: Encoded data will be written to the buffer submitted with -next_out. The length of the compressed data is total_out. +`next_out`. The length of the compressed data is `total_out`. See libaec.h for a detailed description of all relevant structure members and constants. @@ -192,12 +193,12 @@ and output is reversed. ``` It is strongly recommended that the size of the output buffer -(next_out) is a multiple of the storage size in bytes. If the buffer +(`next_out`) is a multiple of the storage size in bytes. If the buffer is not a multiple of the storage size and the buffer gets filled to -the last sample, the error code AEC_MEM_ERROR is returned. +the last sample, the error code `AEC_MEM_ERROR` is returned. -It is essential for decoding that parameters like bits_per_sample, -block_size, rsi, and flags are exactly the same as they were for +It is essential for decoding that parameters like `bits_per_sample`, +`block_size`, `rsi`, and `flags` are exactly the same as they were for encoding. Libaec does not store these parameters in the coded stream so it is up to the calling program to keep the correct parameters between encoding and decoding. @@ -212,9 +213,9 @@ of the parameters. [Consultative Committee for Space Data Systems. Lossless Data Compression. Recommendation for Space Data System Standards, CCSDS 121.0-B-2. Blue Book. Issue 2. Washington, D.C.: CCSDS, May 2012.][1] -[1] http://public.ccsds.org/publications/archive/121x0b2.pdf +[1]: http://public.ccsds.org/publications/archive/121x0b2.pdf [Consultative Committee for Space Data Systems. Lossless Data Compression. Recommendation for Space Data System Standards, CCSDS 120.0-G-3. Green Book. Issue 3. Washington, D.C.: CCSDS, April 2013.][2] -[2] http://public.ccsds.org/publications/archive/120x0g3.pdf +[2]: http://public.ccsds.org/publications/archive/120x0g3.pdf -- cgit v1.2.3