arc/vm/libvda/gpu/mojom/video_decode_accelerator.mojom

// Copyright 2017 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.

// Next MinVersion: 3

// This file defines the mojo interface between Android and Chromium for video
// decoding. Any Mojo callee that returns a value does so by callback.
// However, the caller may receive it by out-param (for sync calls) or
// via callback (for async calls).
// However, we only use callbacks to Reset, Flush and Initialize
// in the present design and don't use for other functions.
// This is mainly because other VDAClient functions and VDA functions are not
// correlated.
// Please don't use this design as a good reference, it is strongly recommended
// in mojom that all the function results are reported by passed callbacks.

module arc.mojom;

import "gfx.mojom";
import "video_common.mojom";

// Information of the bitstream buffer.
struct BitstreamBuffer {
  int32 bitstream_id;
  // This handle is passed and used in Decode().
  // The handle fd is ashmem.
  handle handle_fd;
  uint32 offset;
  uint32 bytes_used;
};

struct Picture {
  int32 picture_buffer_id;
  int32 bitstream_id;
  // the crop rectangle with the picture buffer to be displayed.
  Rect crop_rect;
};

// Format specification of the picture buffer request.
struct PictureBufferFormat {
  // minimal number of buffers required to process the video.
  uint32 min_num_buffers;
  Size coded_size;
};

struct VideoDecodeAcceleratorConfig {
  VideoCodecProfile profile;
  bool secure_mode;
};

// The interface to access the hardware video decoding accelerator. To use
// the decoder, the client first calls Initialize() and must wait for a
// callback with the result. Once done, the client can feed the decoder with
// input bit streams via Decode(). The decoder will call
// VideoDecodeClient::NotifyEndOfBitstreamBuffer() to notify the client that
// it has finished consuming the contents of the buffer.
//
// The decoder will also call VideoDecodeClient::ProvidePictureBuffers to
// ask for output buffers for decoding. The client must provide at least
// PictureBufferFormat::min_num_buffers of output buffers and tell the decoder
// the number by AssignPictureBuffers(). Those output buffers are imported
// one by one by ImportBufferForPicture(). Afterwards, the video decoder will
// writes the decoded output into those output buffers and notify the client
// via PictureReady() to indicate when a buffer is ready to be used. After
// client finish using the decoded buffer, it can return the buffer back to the
// decoder by ReusePictureBuffer(), allowing the buffer to be reused for
// decoding future frames.
//
// For secure playback, the client only holds the dummy buffers for both output
// and input. The protected buffers will be allocated in server side
// and never shared to the client. For input buffers, the client must call
// AllocateProtectedBuffer() for each handle before passing it to Decode().
// The protected buffers will be allocated at the server side for storing
// decrypted input bit streams. For output buffers, the server will allocated
// the protected output buffers when ImportBufferForPicture() is called;
// this will tell the server to import and use the protected buffer instead of
// the dummy buffer.
//
// Deprecated method IDs: 3, 7, 8
// Next method ID: 10
interface VideoDecodeAccelerator {
  [Extensible]
  enum Result {
    SUCCESS = 0,
    ILLEGAL_STATE = 1,
    INVALID_ARGUMENT = 2,
    UNREADABLE_INPUT = 3,
    PLATFORM_FAILURE = 4,
    INSUFFICIENT_RESOURCES = 5,
    CANCELLED = 6,
  };

  // Initializes video decoder accelerator with specific video codec profile.
  // The caller needs to wait for the initialization result (returned by
  // callback) before calling any other methods.
  Initialize@0(VideoDecodeAcceleratorConfig config,
               VideoDecodeClient client) => (Result result);

  // Decodes the content in the shared memory of the bitstream buffer. The
  // callee needs to map the the shared memory to read the content and is
  // responsible to release the shared memory by closing the file descriptor.
  Decode@1(BitstreamBuffer bitstream_buffer);

  // Sets the number of output picture buffers.
  // This releases any buffers in use/imported previously.
  AssignPictureBuffers@2(uint32 count);

  // Imports a buffer to be used by the accelerator with specified
  // |picture_buffer_id|.
  // Releases any previously imported buffer under given |picture_buffer_id|.
  // This should be preceded by a call to AssignPictureBuffers().
  // Calls VDA::ImportBufferForPicture() with |format| and a
  // gfx::GpuMemoryBufferHandle created from |handle_fd| and |planes|.
  [MinVersion=2]
  ImportBufferForPicture@9(int32 picture_buffer_id, HalPixelFormat format,
                           handle handle_fd, array<VideoFramePlane> planes);

  // Returns picture buffer with specified |picture_buffer_id| to be reused by
  // the accelerator.
  ReusePictureBuffer@4(int32 picture_buffer_id);

  // Resets the accelerator, without decoding any pending buffers.
  // When it is done, the callback will be invoked.
  Reset@5() => (Result result);

  // Flushes the accelerator. After all the output buffers pending decode have
  // been returned to client, the callback will be invoked.
  // Flush() can be cancelled by a succeeding Reset(). In that case, the
  // callback is called with Result::CANCELLED.
  Flush@6() => (Result result);
};

// Deprecated method IDs: 0
// Next method ID: 5
interface VideoDecodeClient {

  // Callback to tell client how many and what size of buffers to provide.
  [MinVersion=1]
  ProvidePictureBuffers@4(PictureBufferFormat format);

  // Called to notify the client that |picture| is ready to be displayed.
  // The calls to PictureReady() are in display order and Picture should
  // be displayed in that order.
  PictureReady@1(Picture picture);

  // Called to notify that decoder has decoded the end of the BitstreamBuffer
  // with specified |bitstream_id|.
  NotifyEndOfBitstreamBuffer@2(int32 bitstream_id);

  // Called when an asynchronous error happens, for example, illegal state,
  // error while decoding the stream, or a platform/system error.
  // The errors in Initialize(), Reset() and Flush(), will not be reported here,
  // but will be returned in its callback function.
  NotifyError@3(VideoDecodeAccelerator.Result error);
};