282 lines
12 KiB
Text
282 lines
12 KiB
Text
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/* _______ ____ __ ___ ___
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* \ _ \ \ / \ / \ \ / / ' ' '
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* | | \ \ | | || | \/ | . .
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* | | | | | | || ||\ /| |
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* | | | | | | || || \/ | | ' ' '
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* | | | | | | || || | | . .
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* | |_/ / \ \__// || | |
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* /_______/ynamic \____/niversal /__\ /____\usic /| . . ibliotheque
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* / \
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* / . \
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* deprec.txt - Deprecated functions, why they / / \ \
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* were deprecated, and what to do | < / \_
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* instead. | \/ /\ /
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* \_ / > /
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* | \ / /
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* | ' /
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* \__/
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*/
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**********************************************
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*** How the functions have been deprecated ***
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**********************************************
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GCC 3.1 and later provide a very useful attribute. The following:
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__attribute__((__deprecated__))
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when written alongside a function prototype, variable declaration or type
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definition, will result in a warning from GCC if any such part of the API
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is used. The warning will even tell you where the declaration is, and I
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have inserted comments by all the deprecated declarations, telling you
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what to do.
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Unfortunately, GCC 2.x and 3.0.x and MSVC do not have any means to
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deprecate things. The approach I have taken with these compilers is to
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avoid prototyping the declared functions. This means you will get
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warnings and errors, and they won't be very helpful. If your program
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compiles, you may get strange crashes when you run it, since the compiler
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needs the declarations in order to make sure function calls are carried
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out correctly.
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If you would like the deprecated parts of the API to be declared, you can
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compile with the -DDUMB_DECLARE_DEPRECATED switch for GCC, or the
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-D"DUMB_DECLARE_DEPRECATED" switch for MSVC. This will be accepted by
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GCC 3.x but is unnecessary. Use this switch with other people's projects
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if necessary, but please make the effort to update your own projects to
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use the new API, as the deprecated parts may be removed in the future.
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The rest of this file explains why some parts of the API were deprecated,
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and how to adapt your code.
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**************************************
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*** What happened to DUH_RENDERER? ***
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**************************************
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The DUH_RENDERER struct was designed for rendering audio to an end-user
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format - 8-bit or 16-bit, signed or unsigned, with stereo samples
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interleaved. In order for it to do this, it was built on top of the
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hitherto undocumented DUH_SIGRENDERER struct, which rendered audio in
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DUMB's internal 32-bit signed format with channels (left/right) stored
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separately. The DUH_RENDERER struct contained a pointer to a
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DUH_SIGRENDERER struct, along with some other data like the position and
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number of channels.
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There were then some developments in the API. The DUH_SIGRENDERER struct
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also stored the position and the number of channels, so I decided to write
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functions for returning these. Suddenly there was no need to store them in
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the DUH_RENDERER struct. Before long, the DUH_RENDERER struct contained
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nothing but a pointer to a DUH_SIGRENDERER.
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I decided it would be a good idea to unify the structs. After all, there
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really is no difference between the data stored in each, and it would be
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easy to make duh_render(DUH_RENDERER *dr, ...) and
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duh_render_signal(DUH_SIGRENDERER *sr, ...) work on the same type of
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struct. (Note that duh_render_signal() is now deprecated too; see the next
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section.) It took some deliberation, but I decided I didn't want functions
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to be #defined (it prevents you from using these names for member
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functions in C++ classes), and that meant they had to be defined
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somewhere. Defining redundant functions is a source of bloat, inefficiency
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and general inelegance. After weighing things up, I decided it was better
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to deprecate the redundant functions and have people begin to use the more
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efficient versions, and eventually the redundant functions will be able to
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be removed.
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So why did I choose to keep the more complicated name, DUH_SIGRENDERER?
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The reason has to do with what DUMB will become in the future. Signals are
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an inherent part of the DUH struct and how .duh files will be constructed.
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It will be possible to have multiple signals in a single DUH struct, and
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you will be able to choose which one you want to play (this is the 'sig'
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parameter passed to duh_start_sigrenderer()). But don't hold your breath;
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we still have a long way to go before .duh files will start to appear...
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typedef DUH_SIGRENDERER DUH_RENDERER;
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Wherever you are using DUH_RENDERER in your program, simply replace it
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with DUH_SIGRENDERER. An automated (case-sensitive!) search and replace
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operation should get this done.
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DUH_RENDERER *duh_start_renderer(DUH *duh, int n_channels, long pos);
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Use duh_start_sigrenderer() instead. It takes an extra parameter, 'sig',
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which comes after 'duh' and before 'n_channels'; pass 0 for this. So an
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example would be, replace:
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sr = duh_start_renderer(duh, 2, 0);
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with:
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sr = duh_start_sigrenderer(duh, 0, 2, 0);
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int duh_renderer_get_n_channels(DUH_RENDERER *dr);
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long duh_renderer_get_position(DUH_RENDERER *dr);
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void duh_end_renderer(DUH_RENDERER *dr);
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These are easy enough to fix; all you have to do is replace 'renderer'
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with 'sigrenderer'. So the new functions are:
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int duh_sigrenderer_get_n_channels(DUH_SIGRENDERER *sigrenderer);
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long duh_sigrenderer_get_position(DUH_SIGRENDERER *sigrenderer);
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void duh_end_sigrenderer(DUH_SIGRENDERER *sigrenderer);
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Note that duh_render() has NOT been deprecated. It now uses DUH_SIGRENDERER
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instead of DUH_RENDERER, but its functionality is unchanged. You do not have
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to change calls to this function in any way.
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DUH_RENDERER *duh_renderer_encapsulate_sigrenderer(DUH_SIGRENDERER *sr);
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DUH_SIGRENDERER *duh_renderer_get_sigrenderer(DUH_RENDERER *dr);
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DUH_SIGRENDERER *duh_renderer_decompose_to_sigrenderer(DUH_RENDERER *dr);
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These functions did not exist in the last release of DUMB, so you are
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probably not using them, but they are included here for completeness. All
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you have to do here is unwrap the function, since the structs have been
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unified. So, for instance, replace:
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duh_renderer_encapsulate_sigrenderer(my_sigrenderer)
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with:
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my_sigrenderer
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Simple!
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AL_DUH_PLAYER *al_duh_encapsulate_renderer(DUH_RENDERER *dr,
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float volume, long bufsize, int freq);
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DUH_RENDERER *al_duh_get_renderer(AL_DUH_PLAYER *dp);
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DUH_RENDERER *al_duh_decompose_to_renderer(AL_DUH_PLAYER *dp);
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Again, these functions were not in the last release, so you probably
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aren't using them. Nevertheless, the fix is simple as always: simply
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replace 'renderer' with 'sigrenderer'. So the new functions are:
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AL_DUH_PLAYER *al_duh_encapsulate_sigrenderer(DUH_SIGRENDERER *sr,
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float volume, long bufsize, int freq);
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DUH_SIGRENDERER *al_duh_get_sigrenderer(AL_DUH_PLAYER *dp);
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DUH_SIGRENDERER *al_duh_decompose_to_sigrenderer(AL_DUH_PLAYER *dp);
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*********************
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*** Miscellaneous ***
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*********************
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long duh_render_signal(DUH_SIGRENDERER *sigrenderer,
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float volume, float delta,
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long size, sample_t **samples);
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This function used to return samples in DUMB's internal format. This
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format consisted of 32-bit integers whose 'normal range' was -0x8000 to
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0x7FFF (any samples outside this range would have to be clipped when sent
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to the sound card).
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DUMB's internal format has changed. DUMB still uses 32-bit integers, but
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now the normal range is -0x800000 to 0x7FFFFF. The lowest eight bits are
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discarded at the final stage by duh_render() when you ask for 16-bit
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output. A new function, duh_sigrenderer_get_samples(), will return samples
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in DUMB's new internal format. It takes exactly the same parameters, so
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all you have to do to the call itself is change the name; however, you
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will most likely have to change your code to account for the new
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normalised range.
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duh_render_signal() will still be able to give you the samples in DUMB's
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old internal format, but it is inefficient. You should change your code as
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soon as possible.
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typedef void (*DUH_SIGRENDERER_CALLBACK)(void *data, sample_t **samples,
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int n_channels, long length);
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void duh_sigrenderer_set_callback(DUH_SIGRENDERER *sigrenderer,
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DUH_SIGRENDERER_CALLBACK callback, void *data);
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This callback was intended to allow you to analyse the output. It was by
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no means intended to let you modify the output. For this reason, the names
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have been changed to DUH_SIGRENDERER_ANALYSER_CALLBACK and
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duh_sigrenderer_set_analyser_callback, and the 'samples' parameter to your
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callback should now be specified as follows:
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const sample_t *const *samples
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The first 'const' indicates that you must not modify the samples. The
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second indicates that you must not modify the pointers to each channel.
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There is a second reason why this change was necessary, and it is the one
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described further up for duh_render_signal()'s entry: the format in which
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the samples themselves are stored has changed. They are 256 times as
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large, with a normal range from -0x800000 to 0x7FFFFF. You will most
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likely need to change your code to account for this.
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If you try to call the old function, it will print a message to stderr
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directing you to this file, and it will not install the callback. You
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shouldn't be able to get this far without a compiler warning (or, if you
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don't have GCC 3.1 or later, some compiler errors).
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If you wanted to use this callback to apply a DSP effect, don't worry;
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there is a better way of doing this. It is undocumented, so contact me
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and I shall try to help. Contact details are at the bottom of this file.
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For reference, here are the new definitions:
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typedef void (*DUH_SIGRENDERER_ANALYSER_CALLBACK)(void *data,
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const sample_t *const *samples, int n_channels, long length);
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void duh_sigrenderer_set_analyser_callback(DUH_SIGRENDERER *sigrenderer,
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DUH_SIGRENDERER_ANALYSER_CALLBACK callback, void *data);
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int dumb_resampling_quality;
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This variable has changed meaning. It used to hold a value from 0 to 4,
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whose meaning was as follows:
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0 - aliasing
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1,2 - linear interpolation
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3 - quadratic interpolation
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4 - cubic interpolation
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0,1 - always use a straightforward interpolation algorithm
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2,3,4 - when decimating (increasing the pitch), use a linear average
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algorithm designed to reduce frequencies that would otherwise
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reflect off the Nyquist
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Now the variable only holds values from 0 to 2, and these values have
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preprocessor constants associated with them. The somewhat inappropriate
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quadratic interpolation has been removed. The linear average algorithm has
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also been removed, and may or may not come back; there are probably more
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efficient ways of achieving the same effect, which I shall be
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investigating in the future.
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This change will have hardly any noticeable effect on existing programs.
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Levels 2, 3 and 4 used considerably more processor time because of the
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linear average algorithm. Likewise, Level 2 in the new scheme (cubic) uses
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considerably more processor time than Levels 1 and 0, and Levels 3 and 4
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will behave identically to Level 2.
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******************
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*** Conclusion ***
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******************
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"I conclude that... DUMB is the bestest music player in the world because...
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Complete this sentence in fifteen words or fewer... D'OH!"
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The preceding conclusion formerly appeared in dumb.txt, and is deprecated
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because it's lame.
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Ben Davis
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entheh@users.sf.net
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IRC EFnet #dumb
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See readme.txt for details on using IRC.
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