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Commit 63745973 authored by TreeHugger Robot's avatar TreeHugger Robot Committed by Android (Google) Code Review
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Merge "Camera: Improve timestamping docs"

parents 938bfa36 9d37afcc

camera/ndk/include/camera/NdkCameraMetadataTags.h

+18 −6
Original line number Diff line number Diff line
@@ -8380,12 +8380,16 @@ typedef enum acamera_metadata_enum_acamera_sensor_info_color_filter_arrangement 
// ACAMERA_SENSOR_INFO_TIMESTAMP_SOURCE

typedef enum acamera_metadata_enum_acamera_sensor_info_timestamp_source {

    /**

     * <p>Timestamps from ACAMERA_SENSOR_TIMESTAMP are in nanoseconds and monotonic,

     * but can not be compared to timestamps from other subsystems

     * (e.g. accelerometer, gyro etc.), or other instances of the same or different

     * camera devices in the same system. Timestamps between streams and results for

     * a single camera instance are comparable, and the timestamps for all buffers

     * and the result metadata generated by a single capture are identical.</p>

     * <p>Timestamps from ACAMERA_SENSOR_TIMESTAMP are in nanoseconds and monotonic, but can

     * not be compared to timestamps from other subsystems (e.g. accelerometer, gyro etc.),

     * or other instances of the same or different camera devices in the same system with

     * accuracy. However, the timestamps are roughly in the same timebase as

     * <a href="https://developer.android.com/reference/android/os/SystemClock.html#uptimeMillis">SystemClock#uptimeMillis</a>.  The accuracy is sufficient for tasks

     * like A/V synchronization for video recording, at least, and the timestamps can be

     * directly used together with timestamps from the audio subsystem for that task.</p>

     * <p>Timestamps between streams and results for a single camera instance are comparable,

     * and the timestamps for all buffers and the result metadata generated by a single

     * capture are identical.</p>

     *

     * @see ACAMERA_SENSOR_TIMESTAMP

     */
@@ -8395,6 +8399,14 @@ typedef enum acamera_metadata_enum_acamera_sensor_info_timestamp_source { 
     * <p>Timestamps from ACAMERA_SENSOR_TIMESTAMP are in the same timebase as

     * <a href="https://developer.android.com/reference/android/os/SystemClock.html#elapsedRealtimeNanos">SystemClock#elapsedRealtimeNanos</a>,

     * and they can be compared to other timestamps using that base.</p>

     * <p>When buffers from a REALTIME device are passed directly to a video encoder from the

     * camera, automatic compensation is done to account for differing timebases of the

     * audio and camera subsystems.  If the application is receiving buffers and then later

     * sending them to a video encoder or other application where they are compared with

     * audio subsystem timestamps or similar, this compensation is not present.  In those

     * cases, applications need to adjust the timestamps themselves.  Since <a href="https://developer.android.com/reference/android/os/SystemClock.html#elapsedRealtimeNanos">SystemClock#elapsedRealtimeNanos</a> and <a href="https://developer.android.com/reference/android/os/SystemClock.html#uptimeMillis">SystemClock#uptimeMillis</a> only diverge while the device is asleep, an

     * offset between the two sources can be measured once per active session and applied

     * to timestamps for sufficient accuracy for A/V sync.</p>

     *

     * @see ACAMERA_SENSOR_TIMESTAMP

     */