[FFmpeg-devel] [PATCH] [PATCH] avdevice/avfoundation: add scaleFactor attribute for avfoundation

[sharpbai]

From: sharpbai <tian.bai at duobei.com>

feature: add scaleFactor attribute for avfoundation
added by: siyuan.wang at duobei.com
added by: yiren.li at duobei.com
---
 doc/indevs.texi            | 22 ++++++++++++++++++++++
 libavdevice/avfoundation.m |  6 ++++++
 2 files changed, 28 insertions(+)

diff --git a/doc/indevs.texi b/doc/indevs.texi
index 09e3321..1ba71d7 100644
--- a/doc/indevs.texi
+++ b/doc/indevs.texi
@@ -139,6 +139,13 @@ Capture the mouse pointer. Default is 0.
 @item -capture_mouse_clicks
 Capture the screen mouse clicks. Default is 0.
 
+ at item -scale_factor
+Scale factor for capture the screen. Set this property to scale the buffers
+by a given factor. For example capturing a retina screen which resolution 2880x1800 
+with a scale_factor of 0.5 (or 0.05) produces video buffers at 1440x900 (or 144x90).
+This is useful for reducing captured file size and increasing performance 
+in capturing screen. Default is 1.0 (no scaling).
+
 @end table
 
 @subsection Examples
@@ -169,6 +176,21 @@ Record video from the system default video device using the pixel format bgr0 an
 $ ffmpeg -f avfoundation -pixel_format bgr0 -i "default:none" out.avi
 @end example
 
+ at item
+Capture video from the first screen using the pixel format bgr0 and scaling in half size into out.avi.
+First command use the avfoundation device command to enumerate all the available input devices including
+screens ready to be captured:
+ at example
+$ ffmpeg -f avfoundation -list_devices true -i ""
+ at end example
+Once you've figured out the device index corresponding to the screen to be captured use, run the second
+command with the correct screen device index to execute screen capture. For example on my mac the index
+of "Screen Capture 0" is "1", I should replace @code{-i "<screen_device_index>"} with @code{-i "1"} in the second command.
+ at example
+$ ffmpeg -f avfoundation -pixel_format bgr0 -scale_factor 0.5 -i "<screen_device_index>" out.avi
+ at end example
+
+
 @end itemize
 
 @section bktr
diff --git a/libavdevice/avfoundation.m b/libavdevice/avfoundation.m
index e2ddf47..1196cf3 100644
--- a/libavdevice/avfoundation.m
+++ b/libavdevice/avfoundation.m
@@ -96,6 +96,7 @@ typedef struct
 
     int             capture_cursor;
     int             capture_mouse_clicks;
+    float           scale_factor;
 
     int             list_devices;
     int             video_device_index;
@@ -735,6 +736,10 @@ static int avf_read_header(AVFormatContext *s)
                 capture_screen_input.minFrameDuration = CMTimeMake(ctx->framerate.den, ctx->framerate.num);
             }
 
+            if (ctx->scale_factor > 0.0) {
+                capture_screen_input.scaleFactor = ctx->scale_factor;
+            }
+
 #if !TARGET_OS_IPHONE && __MAC_OS_X_VERSION_MIN_REQUIRED >= 1080
             if (ctx->capture_cursor) {
                 capture_screen_input.capturesCursor = YES;
@@ -1025,6 +1030,7 @@ static const AVOption options[] = {
     { "video_size", "set video size", offsetof(AVFContext, width), AV_OPT_TYPE_IMAGE_SIZE, {.str = NULL}, 0, 0, AV_OPT_FLAG_DECODING_PARAM },
     { "capture_cursor", "capture the screen cursor", offsetof(AVFContext, capture_cursor), AV_OPT_TYPE_INT, {.i64=0}, 0, 1, AV_OPT_FLAG_DECODING_PARAM },
     { "capture_mouse_clicks", "capture the screen mouse clicks", offsetof(AVFContext, capture_mouse_clicks), AV_OPT_TYPE_INT, {.i64=0}, 0, 1, AV_OPT_FLAG_DECODING_PARAM },
+    { "scale_factor", "scale screen factor range", offsetof(AVFContext, scale_factor), AV_OPT_TYPE_FLOAT, {.dbl=1.0}, 0.0, 1.0, AV_OPT_FLAG_DECODING_PARAM },
 
     { NULL },
 };
-- 
2.2.1