141 lines
3.6 KiB
C++
141 lines
3.6 KiB
C++
/*
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* Copyright 2003-2021 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef MPD_ENCODER_INTERFACE_HXX
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#define MPD_ENCODER_INTERFACE_HXX
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#include <cstddef>
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#include <span>
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struct AudioFormat;
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struct Tag;
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class Encoder {
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const bool implements_tag;
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public:
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explicit Encoder(bool _implements_tag) noexcept
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:implements_tag(_implements_tag) {}
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virtual ~Encoder() noexcept = default;
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bool ImplementsTag() const noexcept {
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return implements_tag;
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}
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/**
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* Ends the stream: flushes the encoder object, generate an
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* end-of-stream marker (if applicable), make everything which
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* might currently be buffered available by encoder_read().
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*
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* After this function has been called, the encoder may not be
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* usable for more data, and only Read() and Close() can be
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* called.
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*
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* Throws on error.
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*/
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virtual void End() {
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}
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/**
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* Flushes an encoder object, make everything which might
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* currently be buffered available by Read().
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*
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* Throws on error.
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*/
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virtual void Flush() {
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}
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/**
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* Prepare for sending a tag to the encoder. This is used by
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* some encoders to flush the previous sub-stream, in
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* preparation to begin a new one.
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*
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* Throws on error.
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*/
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virtual void PreTag() {
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}
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/**
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* Sends a tag to the encoder.
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*
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* Instructions: call PreTag(); then obtain flushed data with
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* Read(); finally call Tag().
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*
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* Throws on error.
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*
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* @param tag the tag object
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*/
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virtual void SendTag([[maybe_unused]] const Tag &tag) {
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}
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/**
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* Writes raw PCM data to the encoder.
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*
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* Throws on error.
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*
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* @param data the buffer containing PCM samples
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* @param length the length of the buffer in bytes
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*/
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virtual void Write(std::span<const std::byte> src) = 0;
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/**
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* Reads encoded data from the encoder.
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*
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* Call this repeatedly until no more data is returned.
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*
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* @param buffer a buffer that can be used to write data into
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*
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* @return the portion of the buffer that was filled (but may
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* also point to a different buffer, e.g. one owned by this object)
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*/
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virtual std::span<const std::byte> Read(std::span<std::byte> buffer) noexcept = 0;
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};
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class PreparedEncoder {
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public:
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virtual ~PreparedEncoder() noexcept = default;
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/**
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* Opens the object. You must call this prior to using it.
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* Before you free it, you must call Close(). You may open
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* and close (reuse) one encoder any number of times.
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*
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* After this function returns successfully and before the
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* first encoder_write() call, you should invoke
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* encoder_read() to obtain the file header.
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*
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* Throws on error.
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*
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* @param audio_format the encoder's input audio format; the plugin
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* may modify the struct to adapt it to its abilities
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*/
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virtual Encoder *Open(AudioFormat &audio_format) = 0;
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/**
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* Get mime type of encoded content.
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*
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* @return an constant string, nullptr on failure
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*/
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virtual const char *GetMimeType() const noexcept {
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return nullptr;
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}
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};
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#endif
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