SideBand SurfaceView黑屏分析

•Brief Introduction SideBand

•SideBand Flow

•Tunneled Playback: Analysis Black Frame

 

 •Brief Introduction SideBand

 

App在运行的过程会create Surface, 并会产生对应的BufferQueue及Layer, BufferQueue里面有好几个Slot可以存Graphic Buffer。所以App在绘制的过程就是不断的Dequeue和Enqueue这些Buffer。

SurfaceFlinger会拿这些Enqueue的Buffer去做后续处理, SurfaceFlinger会将各Layer当前的Buffer封裝成imageKHR, 当成texure再去给OpenGL Composer到Framebuffer上, 最后透过HWC的set 里面调用了gralloc, 经过层层呼叫会到OSD driver的pandisplay去显示。

•CompositionType

–HWC_FRAMEBUFFER

–HWC_OVERLAY

–HWC_BACKGROUND

–HWC_FRAMEBUFFER_TARGET

–HWC_SIDEBAND

–HWC_CURSOR_OVERLAY

•HWC_OVERLAY

•HWC_SIDEBAND

l this layer's contents are taken from a sideband buffer stream. Added in HWC_DEVICE_API_VERSION_1_4.

•SideBand Flow

sideband相关类图

sideband flow

 

l non-tunneled video，ACodec的configureCodec中设置sideband的为NULL

 ltunneled-playback，在ACodec的configureTunneledVideoPlayback设置sidebandHandle，非NULL

status_t ACodec::configureTunneledVideoPlayback(
        int32_t audioHwSync, const sp &nativeWindow) {
    native_handle_t* sidebandHandle;

    status_t err = mOMXNode->configureVideoTunnelMode(
            kPortIndexOutput, OMX_TRUE, audioHwSync, &sidebandHandle);
    if (err != OK) {
        ALOGE("configureVideoTunnelMode failed! (err %d).", err);
        return err;
    }

    err = native_window_set_sideband_stream(nativeWindow.get(), sidebandHandle);
    if (err != OK) {
        ALOGE("native_window_set_sideband_stream(%p) failed! (err %d).",
                sidebandHandle, err);
        return err;
    }

    return OK;
}

 •How the hwcomposer handle sideband

l在prepare阶段，hwcomposer会将sideband compositionType修改为OVERLAY

     并调用DRM的driver设置crop ，displayFrame等信息

l因为在OSD no-tunneled playback设置的sideband为NULL

    hwcomposer prepare阶段未做任何处理，合成有GLES来完成

•Tunneled Playback: Analysis Black Frame 

dumpsys SurfaceFlinger

    type   |  handle  | hint | flag | tr | blnd |   format    |     source crop (l,t,r,b)      |          frame         | name

-----------+----------+------+------+----+------+-------------+--------------------------------+------------------------+------

      GLES | 00000000 | 0000 | 0001 | 00 | 0105 | ? ffffffff  |      0,      0,     -1,     -1 |    0,    0, 1920, 1080 | Background for - SurfaceView - com.google.android.exoplayer2.demo/com.google.android.exoplayer2.demo.PlayerActivity#0

       HWC | ad7a4640 | 0002 | 0000 | 00 | 0105 | ? ffffffff  |      0,      0,     -1,     -1 |    0,    0, 1920, 1080 | SurfaceView - com.google.android.exoplayer2.demo/com.google.android.exoplayer2.demo.PlayerActivity#0

      GLES | addcae00 | 0000 | 0000 | 00 | 0105 | RGBA_8888   |      0,      0,   1920,   1080 |    0,    0, 1920, 1080 | com.google.android.exoplayer2.demo/com.google.android.exoplayer2.demo.PlayerActivity#0

 FB TARGET | addc96e0 | 0000 | 0000 | 00 | 0105 | RGBA_8888   |      0,      0,   1920,   1080 |    0,    0, 1920, 1080 | HWC_FRAMEBUFFER_TARGET

可以发现tunneled video playback在SurfaceFlinger进行合成时，多了一层Background SurfaceView，将surfaceview给遮住了，查看SurfaceView的isOpaque = 0，这个数值异常，

在SurfaceFlinger的rebuildLayerStacks中会去computeVisibleRegions，其中就会使用到这个参数isOpaque，因为其为0；这样就导致在计算background surfaceview时，就是全屏了，因为surfaceview没有将background遮住

定位到isOpaque这个函数，查看Google源码发现，Google在8.1版本对此处有修改

Sync过来这个修改，问题就解了