// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CHROMECAST_PUBLIC_MEDIA_EXTERNAL_AUDIO_DECODER_H_
#define CHROMECAST_PUBLIC_MEDIA_EXTERNAL_AUDIO_DECODER_H_
#include <cstddef>
#include "cast_decoder_buffer.h"
#include "chromecast_export.h"
#include "decoder_config.h"
namespace chromecast {
namespace media {
// The external audio decoder is an optional dynamically-loaded shared library.
// The library is loaded as "libcast_external_decoder.so" from the cast_shell
// shared library search path. See below for the functions that the library
// must export.
// Interface for additional audio decoder functionality. ExternalAudioDecoder
// always decodes to planar float format.
class ExternalAudioDecoder {
public:
class Delegate {
public:
// Allocates a buffer to write decoded audio into. The caller may write
// up to |bytes| bytes of decoded audio into the returned buffer, in the
// desired output format. To avoid memory leaks, OnDecodedBuffer() must be
// called for every allocated buffer. It is an error to call AllocateBuffer
// twice in a row without calling OnDecodedBuffer() in between.
virtual void* AllocateBuffer(size_t bytes) = 0;
// Informs the delegate that |decoded_size_bytes| of decoded audio data have
// been written into the buffer most recently returned by AllocateBuffer().
// |decoded_size_bytes| may be 0. |config| is the config of the decoded
// audio. It is assumed that the config is the same for all
// OnDecodedBuffer() calls that occur within a single call to
// ExternalAudioDecoder::Decode(), but the config may change between calls
// to Decode(). Decoded audio must be in planar float format.
virtual void OnDecodedBuffer(size_t decoded_size_bytes,
const AudioConfig& config) = 0;
protected:
virtual ~Delegate() = default;
};
// Returns the expected number of channels in the decoded audio. This is
// called immediately after construction. Returns 0 if the number of channels
// is not known.
virtual int GetNumOutputChannels() = 0;
// Decodes an audio buffer. The implementation of this method should call
// the delegate's AllocateBuffer() method to allocate a buffer, write some
// decoded data to the buffer, and then call the delegate's OnDecodedBuffer()
// method. This may be done 0 or more times per call to Decode(). All delegate
// methods must be called synchronously from within Decode(). Returns |false|
// if an error occurred while decoding.
virtual bool Decode(const CastDecoderBuffer& buffer) = 0;
protected:
virtual ~ExternalAudioDecoder() = default;
};
// The external decoder library must export the following functions:
// Returns |true| if |config| is supported by the external decoder library,
// |false| otherwise. An ExternalAudioDecoder instance will be created for any
// stream where |true| is returned for the config.
extern "C" CHROMECAST_EXPORT bool ExternalAudioDecoder_IsSupportedConfig(
const AudioConfig& config);
// Creates an external audio decoder. The |delegate| is guaranteed to outlive
// the returned decoder instance. The returned decoder will be deleted by
// calling ExternalAudioDecoder_DeleteDecoder().
extern "C" CHROMECAST_EXPORT ExternalAudioDecoder*
ExternalAudioDecoder_CreateDecoder(ExternalAudioDecoder::Delegate* delegate,
const AudioConfig& config);
// Deletes an external audio decoder.
extern "C" CHROMECAST_EXPORT void ExternalAudioDecoder_DeleteDecoder(
ExternalAudioDecoder* decoder);
} // namespace media
} // namespace chromecast
#endif // CHROMECAST_PUBLIC_MEDIA_EXTERNAL_AUDIO_DECODER_H_
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