qzdoom/dumb/docs/deprec.txt

/*  _______         ____    __         ___    ___
 * \    _  \       \    /  \  /       \   \  /   /       '   '  '
 *  |  | \  \       |  |    ||         |   \/   |         .      .
 *  |  |  |  |      |  |    ||         ||\  /|  |
 *  |  |  |  |      |  |    ||         || \/ |  |         '  '  '
 *  |  |  |  |      |  |    ||         ||    |  |         .      .
 *  |  |_/  /        \  \__//          ||    |  |
 * /_______/ynamic    \____/niversal  /__\  /____\usic   /|  .  . ibliotheque
 *                                                      /  \
 *                                                     / .  \
 * deprec.txt - Deprecated functions, why they        / / \  \
 *              were deprecated, and what to do      | <  /   \_
 *              instead.                             |  \/ /\   /
 *                                                    \_  /  > /
 *                                                      | \ / /
 *                                                      |  ' /
 *                                                       \__/
 */


**********************************************
*** How the functions have been deprecated ***
**********************************************


   GCC 3.1 and later provide a very useful attribute. The following:

      __attribute__((__deprecated__))

   when written alongside a function prototype, variable declaration or type
   definition, will result in a warning from GCC if any such part of the API
   is used. The warning will even tell you where the declaration is, and I
   have inserted comments by all the deprecated declarations, telling you
   what to do.

   Unfortunately, GCC 2.x and 3.0.x and MSVC do not have any means to
   deprecate things. The approach I have taken with these compilers is to
   avoid prototyping the deprecated parts of the API. This means you will get
   warnings and errors, and they won't be very helpful. If your program
   compiles, you may get strange crashes when you run it, since the compiler
   needs the declarations in order to make sure function calls are carried
   out correctly.

   If you would like the deprecated parts of the API to be declared, you can
   compile with the -DDUMB_DECLARE_DEPRECATED switch for GCC, or the
   -D"DUMB_DECLARE_DEPRECATED" switch for MSVC. This will be accepted by
   GCC 3.x but is unnecessary. Use this switch with other people's projects
   if necessary, but please make the effort to update your own projects to
   use the new API, as the deprecated parts may be removed in the future.

   The rest of this file explains why some parts of the API were deprecated,
   and how to adapt your code.


**************************************
*** What happened to DUH_RENDERER? ***
**************************************


   The DUH_RENDERER struct was designed for rendering audio to an end-user
   format - 8-bit or 16-bit, signed or unsigned, with stereo samples
   interleaved. In order for it to do this, it was built on top of the
   hitherto undocumented DUH_SIGRENDERER struct, which rendered audio in
   DUMB's internal 32-bit signed format with channels (left/right) stored
   separately. The DUH_RENDERER struct contained a pointer to a
   DUH_SIGRENDERER struct, along with some other data like the position and
   number of channels.

   There were then some developments in the API. The DUH_SIGRENDERER struct
   also stored the position and the number of channels, so I decided to write
   functions for returning these. Suddenly there was no need to store them in
   the DUH_RENDERER struct. Before long, the DUH_RENDERER struct contained
   nothing but a pointer to a DUH_SIGRENDERER.

   I decided it would be a good idea to unify the structs. After all, there
   really is no difference between the data stored in each, and it would be
   easy to make duh_render(DUH_RENDERER *dr, ...) and
   duh_render_signal(DUH_SIGRENDERER *sr, ...) work on the same type of
   struct. (Note that duh_render_signal() is now deprecated too; see the next
   section.) It took some deliberation, but I decided I didn't want functions
   to be #defined (it prevents you from using these names for member
   functions in C++ classes), and that meant they had to be defined
   somewhere. Defining redundant functions is a source of bloat, inefficiency
   and general inelegance. After weighing things up, I decided it was better
   to deprecate the redundant functions and have people begin to use the more
   efficient versions, and eventually the redundant functions will be able to
   be removed.

   So why did I choose to keep the more complicated name, DUH_SIGRENDERER?
   The reason has to do with what DUMB will become in the future. Signals are
   an inherent part of the DUH struct and how .duh files will be constructed.
   It will be possible to have multiple signals in a single DUH struct, and
   you will be able to choose which one you want to play (this is the 'sig'
   parameter passed to duh_start_sigrenderer()). But don't hold your breath;
   we still have a long way to go before .duh files will start to appear...


typedef DUH_SIGRENDERER DUH_RENDERER;

   Wherever you are using DUH_RENDERER in your program, simply replace it
   with DUH_SIGRENDERER. An automated (case-sensitive!) search and replace
   operation should get this done.


DUH_RENDERER *duh_start_renderer(DUH *duh, int n_channels, long pos);

   Use duh_start_sigrenderer() instead. It takes an extra parameter, 'sig',
   which comes after 'duh' and before 'n_channels'; pass 0 for this. So an
   example would be, replace:

      sr = duh_start_renderer(duh, 2, 0);

   with:

      sr = duh_start_sigrenderer(duh, 0, 2, 0);


int duh_renderer_get_n_channels(DUH_RENDERER *dr);
long duh_renderer_get_position(DUH_RENDERER *dr);
void duh_end_renderer(DUH_RENDERER *dr);

   These are easy enough to fix; all you have to do is replace 'renderer'
   with 'sigrenderer'. So the new functions are:

      int duh_sigrenderer_get_n_channels(DUH_SIGRENDERER *sigrenderer);
      long duh_sigrenderer_get_position(DUH_SIGRENDERER *sigrenderer);
      void duh_end_sigrenderer(DUH_SIGRENDERER *sigrenderer);


Note that duh_render() has NOT been deprecated. It now uses DUH_SIGRENDERER
instead of DUH_RENDERER, but its functionality is unchanged. You do not have
to change calls to this function in any way.


DUH_RENDERER *duh_renderer_encapsulate_sigrenderer(DUH_SIGRENDERER *sr);
DUH_SIGRENDERER *duh_renderer_get_sigrenderer(DUH_RENDERER *dr);
DUH_SIGRENDERER *duh_renderer_decompose_to_sigrenderer(DUH_RENDERER *dr);

   These functions did not exist in the last release of DUMB, so you are
   probably not using them, but they are included here for completeness. All
   you have to do here is unwrap the function, since the structs have been
   unified. So, for instance, replace:

      duh_renderer_encapsulate_sigrenderer(my_sigrenderer)

   with:

      my_sigrenderer

   Simple!


AL_DUH_PLAYER *al_duh_encapsulate_renderer(DUH_RENDERER *dr,
                                       float volume, long bufsize, int freq);
DUH_RENDERER *al_duh_get_renderer(AL_DUH_PLAYER *dp);
DUH_RENDERER *al_duh_decompose_to_renderer(AL_DUH_PLAYER *dp);

   Again, these functions were not in the last release, so you probably
   aren't using them. Nevertheless, the fix is simple as always: simply
   replace 'renderer' with 'sigrenderer'. So the new functions are:

      AL_DUH_PLAYER *al_duh_encapsulate_sigrenderer(DUH_SIGRENDERER *sr,
                                       float volume, long bufsize, int freq);
      DUH_SIGRENDERER *al_duh_get_sigrenderer(AL_DUH_PLAYER *dp);
      DUH_SIGRENDERER *al_duh_decompose_to_sigrenderer(AL_DUH_PLAYER *dp);


*********************
*** Miscellaneous ***
*********************


long duh_render_signal(DUH_SIGRENDERER *sigrenderer,
                       float volume, float delta,
                       long size, sample_t **samples);

   This function used to return samples in DUMB's internal format. This
   format consisted of 32-bit integers whose 'normal range' was -0x8000 to
   0x7FFF (any samples outside this range would have to be clipped when sent
   to the sound card).

   DUMB's internal format has changed. DUMB still uses 32-bit integers, but
   now the normal range is -0x800000 to 0x7FFFFF. The lowest eight bits are
   discarded at the final stage by duh_render() when you ask for 16-bit
   output. A new function, duh_sigrenderer_get_samples(), will return samples
   in DUMB's new internal format. It takes exactly the same parameters, so
   all you have to do to the call itself is change the name; however, you
   will most likely have to change your code to account for the new
   normalised range.

   duh_render_signal() will still be able to give you the samples in DUMB's
   old internal format, but it is inefficient. You should change your code as
   soon as possible.


typedef void (*DUH_SIGRENDERER_CALLBACK)(void *data, sample_t **samples,
                                         int n_channels, long length);

void duh_sigrenderer_set_callback(DUH_SIGRENDERER *sigrenderer,
                              DUH_SIGRENDERER_CALLBACK callback, void *data);

   This callback was intended to allow you to analyse the output. It was by
   no means intended to let you modify the output. For this reason, the names
   have been changed to DUH_SIGRENDERER_ANALYSER_CALLBACK and
   duh_sigrenderer_set_analyser_callback, and the 'samples' parameter to your
   callback should now be specified as follows:

      const sample_t *const *samples

   The first 'const' indicates that you must not modify the samples. The
   second indicates that you must not modify the pointers to each channel.

   There is a second reason why this change was necessary, and it is the one
   described further up for duh_render_signal()'s entry: the format in which
   the samples themselves are stored has changed. They are 256 times as
   large, with a normal range from -0x800000 to 0x7FFFFF. You will most
   likely need to change your code to account for this.

   If you try to call the old function, it will print a message to stderr
   directing you to this file, and it will not install the callback. You
   shouldn't be able to get this far without a compiler warning (or, if you
   don't have GCC 3.1 or later, some compiler errors).

   If you wanted to use this callback to apply a DSP effect, don't worry;
   there is a better way of doing this. It is undocumented, so contact me
   and I shall try to help. Contact details are at the bottom of this file.

   For reference, here are the new definitions:

   typedef void (*DUH_SIGRENDERER_ANALYSER_CALLBACK)(void *data,
                const sample_t *const *samples, int n_channels, long length);

   void duh_sigrenderer_set_analyser_callback(DUH_SIGRENDERER *sigrenderer,
                     DUH_SIGRENDERER_ANALYSER_CALLBACK callback, void *data);


int dumb_resampling_quality;

   This variable has changed meaning. It used to hold a value from 0 to 4,
   whose meaning was as follows:

        0   - aliasing
       1,2  - linear interpolation
        3   - quadratic interpolation
        4   - cubic interpolation

       0,1  - always use a straightforward interpolation algorithm
      2,3,4 - when decimating (increasing the pitch), use a linear average
              algorithm designed to reduce frequencies that would otherwise
              reflect off the Nyquist

   Now the variable only holds values from 0 to 2, and these values have
   preprocessor constants associated with them. The somewhat inappropriate
   quadratic interpolation has been removed. The linear average algorithm has
   also been removed, and may or may not come back; there are probably more
   efficient ways of achieving the same effect, which I shall be
   investigating in the future.

   This change will have hardly any noticeable effect on existing programs.
   Levels 2, 3 and 4 used considerably more processor time because of the
   linear average algorithm. Likewise, Level 2 in the new scheme (cubic) uses
   considerably more processor time than Levels 1 and 0, and Levels 3 and 4
   will behave identically to Level 2.


******************
*** Conclusion ***
******************


"I conclude that... DUMB is the bestest music player in the world because...
Complete this sentence in fifteen words or fewer... D'OH!"

The preceding conclusion formerly appeared in dumb.txt, and is deprecated
because it's lame.


Ben Davis
entheh@users.sf.net
IRC EFnet #dumb
See readme.txt for details on using IRC.