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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MEDIA_BASE_VIDEO_DECODER_H_
#define MEDIA_BASE_VIDEO_DECODER_H_
#include <string>
#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "media/base/decode_status.h"
#include "media/base/media_export.h"
#include "media/base/pipeline_status.h"
#include "ui/gfx/geometry/size.h"
namespace media {
class CdmContext;
class DecoderBuffer;
class VideoDecoderConfig;
class VideoFrame;
class MEDIA_EXPORT VideoDecoder {
public:
// Callback for VideoDecoder initialization.
using InitCB = base::Callback<void(bool success)>;
// Callback for VideoDecoder to return a decoded frame whenever it becomes
// available. Only non-EOS frames should be returned via this callback.
using OutputCB = base::Callback<void(const scoped_refptr<VideoFrame>&)>;
// Callback type for Decode(). Called after the decoder has completed decoding
// corresponding DecoderBuffer, indicating that it's ready to accept another
// buffer to decode.
using DecodeCB = base::Callback<void(DecodeStatus)>;
// Callback for whenever the key needed to decrypt the stream is not
// available. May be called at any time after Initialize().
using WaitingForDecryptionKeyCB = base::RepeatingClosure;
VideoDecoder();
// Returns the name of the decoder for logging and decoder selection purposes.
// This name should be available immediately after construction (e.g. before
// Initialize() is called). It should also be stable in the sense that the
// name does not change across multiple constructions.
virtual std::string GetDisplayName() const = 0;
// Returns true if the implementation is expected to be implemented by the
// platform. The value should be available immediately after construction and
// should not change within the lifetime of a decoder instance. The value is
// used for logging and metrics recording.
//
// TODO(sandersd): Use this to decide when to switch to software decode for
// low-resolution videos. https://crbug.com/684792
virtual bool IsPlatformDecoder() const;
// Initializes a VideoDecoder with the given |config|, executing the
// |init_cb| upon completion. |output_cb| is called for each output frame
// decoded by Decode().
//
// If |low_delay| is true then the decoder is not allowed to queue frames,
// except for out-of-order frames, i.e. if the next frame can be returned it
// must be returned without waiting for Decode() to be called again.
// Initialization should fail if |low_delay| is true and the decoder cannot
// satisfy the requirements above.
//
// |cdm_context| can be used to handle encrypted buffers. May be null if the
// stream is not encrypted.
//
// |waiting_for_decryption_key_cb| is called whenever the key needed to
// decrypt the stream is not available.
//
// Note:
// 1) The VideoDecoder will be reinitialized if it was initialized before.
// Upon reinitialization, all internal buffered frames will be dropped.
// 2) This method should not be called during pending decode or reset.
// 3) No VideoDecoder calls should be made before |init_cb| is executed.
// 4) VideoDecoders should take care to run |output_cb| as soon as the frame
// is ready (i.e. w/o thread trampolining) since it can strongly affect frame
// delivery times with high-frame-rate material. See Decode() for additional
// notes.
virtual void Initialize(
const VideoDecoderConfig& config,
bool low_delay,
CdmContext* cdm_context,
const InitCB& init_cb,
const OutputCB& output_cb,
const WaitingForDecryptionKeyCB& waiting_for_decryption_key_cb) = 0;
// Requests a |buffer| to be decoded. The status of the decoder and decoded
// frame are returned via the provided callback. Some decoders may allow
// decoding multiple buffers in parallel. Callers should call
// GetMaxDecodeRequests() to get number of buffers that may be decoded in
// parallel.
//
// Implementations guarantee that the |decode_cb| will not be called from
// within this method, and that it will be called even if Decode() is never
// called again.
//
// After decoding is finished the decoder calls |output_cb| specified in
// Initialize() for each decoded frame. |output_cb| may be called before or
// after |decode_cb|, including before Decode() returns.
//
// If |buffer| is an EOS buffer then the decoder must be flushed, i.e.
// |output_cb| must be called for each frame pending in the queue and
// |decode_cb| must be called after that. Callers will not call Decode()
// again until after the flush completes.
virtual void Decode(scoped_refptr<DecoderBuffer> buffer,
const DecodeCB& decode_cb) = 0;
// Resets decoder state. All pending Decode() requests will be finished or
// aborted before |closure| is called.
// Note: No VideoDecoder calls should be made before |closure| is executed.
virtual void Reset(const base::Closure& closure) = 0;
// Returns true if the decoder needs bitstream conversion before decoding.
virtual bool NeedsBitstreamConversion() const;
// Returns true if the decoder currently has the ability to decode and return
// a VideoFrame. Most implementations can allocate a new VideoFrame and hence
// this will always return true. Override and return false for decoders that
// use a fixed set of VideoFrames for decoding.
virtual bool CanReadWithoutStalling() const;
// Returns maximum number of parallel decode requests.
virtual int GetMaxDecodeRequests() const;
// Returns the recommended number of threads for software video decoding. If
// the --video-threads command line option is specified and is valid, that
// value is returned. Otherwise |desired_threads| is clamped to the number of
// logical processors and then further clamped to
// [|limits::kMinVideoDecodeThreads|, |limits::kMaxVideoDecodeThreads|].
static int GetRecommendedThreadCount(int desired_threads);
protected:
// Deletion is only allowed via Destroy().
virtual ~VideoDecoder();
private:
friend struct std::default_delete<VideoDecoder>;
// Fires any pending callbacks, stops and destroys the decoder. After this
// call, external resources (e.g. raw pointers) |this| holds might be
// invalidated immediately. So if the decoder is destroyed asynchronously
// (e.g. DeleteSoon), external resources must be released in this call.
virtual void Destroy();
DISALLOW_COPY_AND_ASSIGN(VideoDecoder);
};
} // namespace media
namespace std {
// Specialize std::default_delete to call Destroy().
template <>
struct MEDIA_EXPORT default_delete<media::VideoDecoder> {
constexpr default_delete() = default;
template <typename U,
typename = typename std::enable_if<
std::is_convertible<U*, media::VideoDecoder*>::value>::type>
default_delete(const default_delete<U>& d) {}
void operator()(media::VideoDecoder* ptr) const;
};
} // namespace std
#endif // MEDIA_BASE_VIDEO_DECODER_H_