SurfaceView Canvas 在 4K Android TV 上以 1080p 渲染

Question

我正在尝试使用 SurfaceView 在 4K Android TV 设备（运行 Android 9 的 Nvidia Shield TV）上以原始分辨率呈现 3840x2160 位图。

根据Android 6 release notes，我应该能够将preferredDisplayModeId 设置为支持4K 分辨率的Display.Mode，以便让我的SurfaceView 以4K 渲染。但是，似乎即使设置了preferredDisplayModeId，我认为提供给onDraw方法的Canvas也只有1920x1080。尝试将 3840x2160 位图绘制到它会导致图像缩小到 1080p，然后再放大到 2160p，在此过程中会丢失信息。

这是我Activity的相关代码：

windowManager.defaultDisplay.supportedModes.forEach {
    if (it.physicalHeight == 2160 && it.refreshRate > 60) {
        val params = window.attributes
        params.preferredDisplayModeId = it.modeId
        window.attributes = params
    }
}

setContentView(R.layout.main)

我的布局包含扩展SurfaceView 的自定义视图。自定义视图有一个 onDraw 方法，如下所示：

override fun onDraw(canvas: Canvas) {
    canvas.drawBitmap(
        currentImage,
        Rect(0, 0, currentImage!!.width, currentImage!!.height),
        canvas.clipBounds,
        null
    )
}

canvas.clipBounds 是Rect(0, 0 - 1920, 1080)，所以当它尝试渲染完整的位图时，它必须缩小它以适应。

当我的SurfaceView 被渲染时，这是adb shell dumpsys SurfaceFlinger 的一些输出：

Display 0 HWC layers:
-------------------------------------------------------------------------------
 Layer name
           Z |  Comp Type |   Disp Frame (LTRB) |          Source Crop (LTRB)
-------------------------------------------------------------------------------
 com.google.android.tvlauncher/com.google.android.tvlauncher.MainActivity#0
  rel      0 |     Device |    0    0 3840 2160 |    0.0    0.0 1920.0 1080.0
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Dim Layer for - Task=580#0
  rel     -1 |     Client |    0    0 3840 2160 |    0.0    0.0   -1.0   -1.0
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 com.android.tv.settings/com.android.tv.settings.MainSettings#0
  rel      0 |     Client |    0    0 3840 2160 |    0.0    0.0 1920.0 1080.0
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Background for -SurfaceView - Sys2023:dream#0
  rel     -3 |     Client |    0    0 3840 2160 |    0.0    0.0   -1.0   -1.0
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Sys2023:dream#0
  rel      0 |     Client |    0    0 3840 2160 |    0.0    0.0 1920.0 1080.0
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Allocated buffers:
0x513aff00: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | Sys2023:dream#0
0x5333f300:    4.00 KiB |   16 (  64) x   16 |    1 |        1 | 0x1a00 | FakeFramebuffer
0x53340f80: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.android.tv.settings/com.android.tv.settings.MainSettings#0
0x53341280: 32400.00 KiB | 3840 (3840) x 2160 |    1 |        1 | 0x1b00 | FramebufferSurface
0x53341700: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.google.android.tvlauncher/com.google.android.tvlauncher.MainActivity#0
0x53341880: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.google.android.tvlauncher/com.google.android.tvlauncher.MainActivity#0
0x53341d00: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.android.tv.settings/com.android.tv.settings.MainSettings#0
0x53341e80: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.google.android.tvlauncher/com.google.android.tvlauncher.MainActivity#0
0x55d35480: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.android.systemui.ImageWallpaper#0
0x55d35900: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.android.tv.settings/com.android.tv.settings.MainSettings#0
0x55d35d80: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | Sys2023:dream#0
0x55d37580: 32400.00 KiB | 3840 (3840) x 2160 |    1 |        1 | 0x1b00 | FramebufferSurface
Total allocated (estimate): 137704.00 KB

作为比较，当我的应用渲染 ExoPlayer 视图时，输出相同，它正确渲染了 4K SurfaceView：

Display 0 HWC layers:
-------------------------------------------------------------------------------
 Layer name
           Z |  Comp Type |   Disp Frame (LTRB) |          Source Crop (LTRB)
-------------------------------------------------------------------------------
 SurfaceView - Sys2023:dream#0
  rel     -2 |     Device |    0    0 3840 2160 |    0.0    0.0 3840.0 2160.0
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Sys2023:dream#0
  rel      0 |     Device |    0    0 3840 2160 |    0.0    0.0 1920.0 1080.0
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Allocated buffers:
0x513af180: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x513af300: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x513afc00: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x513afd80: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | Sys2023:dream#0
0x5333f300:    4.00 KiB |   16 (  64) x   16 |    1 |        1 | 0x1a00 | FakeFramebuffer
0x53340f80: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.android.tv.settings/com.android.tv.settings.MainSettings#0
0x53341280: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x53341400: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x53341700: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.google.android.tvlauncher/com.google.android.tvlauncher.MainActivity#0
0x53341880: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.google.android.tvlauncher/com.google.android.tvlauncher.MainActivity#0
0x53341a00: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | Sys2023:dream#0
0x53341d00: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.android.tv.settings/com.android.tv.settings.MainSettings#0
0x53341e80: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.google.android.tvlauncher/com.google.android.tvlauncher.MainActivity#0
0x55d35480: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.android.systemui.ImageWallpaper#0
0x55d35900: 8100.00 KiB | 1920 (1920) x 1080 |    1 |        1 | 0xb00 | com.android.tv.settings/com.android.tv.settings.MainSettings#0
0x55d35f00: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x55d36080: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x55d36200: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x55d36380: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x55d36500: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x55d36680: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x55d36800: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x55d36f80: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x55d37100: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
0x55d37280: unknown     | 3840 (3840) x 2160 |    1 |      12B | 0x900 | SurfaceView - Sys2023:dream#0
Total allocated (estimate): 72904.00 KB

当显示ExoPlayer 时，您可以看到SurfaceView 缓冲区正确为3840x2160，但在使用我的自定义视图时，它似乎没有分配任何SurfaceView 缓冲区。

Answer 1

在尝试使用画布绘制之前设置 SurfaceView 的分辨率。

getHolder().setFixedSize(3840, 2160);

Answer 2

我会开始使用 ExoPlayer 来展示你需要的东西。这应该是可能的。

但是，我认为您没有正确分配画布，我想您是否使用包含 4k 的 rect(args) ？似乎您正在创建错误的画布，或者因为如果您在 nvidia shield 上运行并且 afaik 我的 shiled 运行 android 在 1080p 上运行，并且如果您通过 getter 请求仍然旧，画布将获得该大小。

在我看来，最简单的解决方案是使用 ExoPlayer。