Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

These were used because the entropy coder originally came from
 outside libcelt, and thus did not have a common type system.
It's now undergone enough modification that it's not ever likely to
 be used as-is in another codec without some porting effort, so
 there's no real reason to maintain the typedefs separately.
Hopefully we'll replace these all again somedate with a common set
 of Opus typedefs, but for now this will do.

This fixes an issue caused by commit 6c8acbf1, which moved the
 ec_ilog() prototype from entcode.h to ecintrin.h, where the
 ec_uint32 typedef was not yet available.
Thanks to John Ridges for the report.

Got authorization from all copyright holders

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

This unifies the byte buffer, encoder, and decoder into a single
 struct.
The common encoder and decoder functions (such as ec_tell()) can
 operate on either one, simplifying code which uses both.
The precision argument to ec_tell() has been removed.
It now comes in two precisions:
  ec_tell() gives 1 bit precision in two operations, and
  ec_tell_frac() gives 1/8th bit precision in... somewhat more.
ec_{enc|dec}_bit_prob() were removed (they are no longer needed).
Some of the byte buffer access functions were made static and
 removed from the cross-module API.
All of the code in rangeenc.c and rangedec.c was merged into
 entenc.c and entdec.c, respectively, as we are no longer
 considering alternative backends.
rangeenc.c and rangede.c have been removed entirely.

This passes make check, after disabling the modes that we removed
 support for in cf5d3a8c.

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

This renames ec_dec_cdf() to ec_dec_icdf(), and changes the
 functionality to use an "inverse" CDF table, where
 icdf[i]=ft-cdf[i+1].
The first entry is omitted entirely.
It also adds a corresonding ec_enc_icdf() to the encoder, which uses
 the same table.
One could use ec_encode_bin() by converting the values in the tables
 back to normal CDF values, but the icdf[] table already has them in
 the form ec_encode_bin() wants to use them, so there's no reason to
 translate them and then translate them back.

This is done primarily to allow SILK to use the range coder with
 8-bit probability tables containing cumulative frequencies that
 span the full range 0...256.
With an 8-bit table, the final 256 of a normal CDF becomes 0 in the
 "inverse" CDF.
It's the 0 at the start of a normal CDF which would become 256, but
 this is the value we omit, as it already has to be special-cased in
 the encoder, and is not used at all in the decoder.

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

For our current usage, this doesn't matter, but is more consistent
 with the rest of the API.
We may want to reduce this to an unsigned char[], but I'd rather
 coordinate that optimization with SILK's planned reduction to
 8-bit CDFs, as we may be able to use the same code.

This simplifies a good bit of the error handling, and should make it
 impossible to overrun the buffer in the encoder or decoder, while
 still allowing tell() to operate correctly after a bust.
The encoder now tries to keep the range coder data intact after a
 bust instead of corrupting it with extra bits data, though this is
 not a guarantee (too many extra bits may have already been flushed).
It also now correctly reports errors when the bust occurs merging the
 last byte of range coder and extra bits.

A number of abstraction barrier violations were cleaned up, as well.
This patch also includes a number of minor performance improvements:
 ec_{enc|dec}_bits() in particular should be much faster.

Finally, tf_select was changed to be coded with the range coder
 rather than extra bits, so that it is at the front of the packet
 (for unequal error protection robustness).

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

All of our usage of ec_{enc|dec}_bit_prob had the probability of a
 "one" being a power of two.
This adds a new ec_{enc|dec}_bit_logp() function that takes this
 explicitly into account.
It introduces less rounding error than the bit_prob version, does not
 require 17-bit integers to be emulated by ec_{encode|decode}_bin(),
 and does not require any multiplies or divisions at all.
It is exactly equivalent to
 ec_encode_bin(enc,_val?0:(1<<_logp)-1,(1<<_logp)-(_val?1:0),1<<_logp)

The old ec_{enc|dec}_bit_prob functions are left in place for now,
 because I am not sure if SILK is still using them or not when
 combined in Opus.

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

It turns out to be more convenient to store dif=low+rng-code-1
 instead of dif=low+rng-code.
This gets rid of a decrement in the normal decode path, replaces a
 decrement and an "and" in the normalization loop with a single
 add, and makes it clear that the new ec_dec_cdf() will not result
 in an infinite loop.
This does not change the bitstream.

This decodes a value encoded with ec_encode_bin() without using any
 divisions.
It is only meant for small alphabets.
If a symbol can take on a large number of possible values, a binary
 search would be better.

This patch also converts spread_decision to use it, since it is
 faster and introduces less rounding error to encode a single
 decision for the entire value than to encode it a bit at a time.

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

Change ec_{enc|dec}_bit_prob to take probabilities in units of 1/65536 instead of 1/256. This allows them to use a single 16x16->32 multiply instead of a 24x8->32 multiply. Also change the time-frequency resolution flag coding to ensure that "0" is always the most-probable symbol (i.e., that prob("1")<50%), as that's where all the rounding error accumulates.

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

Provide direct implementations ec_{enc|dec}_bit_prob() that do not require a division instead of using the normal entropy coder path. This should be exactly equivalent to the existing code.

by POSIX. The other _t types that are not part of the API are still there
for now. Also, got rid of all that was left of the 64-bit types.

original ec_encode_bin()/ec_decode_bin() to optimize performance when ft is
a power of two.

Making it so all the information encoded directly with ec_enc_bits() gets
stored at the end of the stream, without going through the range coder. This
should be both faster and reduce the effects of bit errors.

Conflicts:

	tests/ectest.c

Signed-off-by: Timothy B. Terriberry <tterribe@xiph.org>

required) and using it in ec_{en|de}c_bits()

especially now that we have a custom version of that code anyway. Moved
the test code to tests/

tterribe authored 17 years ago and Jean-Marc Valin committed 17 years ago

Add ec_dec_tell() to report the same information as ec_enc_tell() decode side. Remove ec_enc_tell() and replace it with ec_enc_tellf(): just request 0 fractional bits if you want an integer value.

git-svn-id: http://svn.xiph.org/trunk/ghost@14394 0101bb08-14d6-0310-b084-bc0e0c8e3800

Updated broken paper URLs.
Cleaned up non-multiply-free range coder documentation (e.g., stop claiming
it's multiply-free).