Update the documentation regarding the default media backend

We have restrict the list of platforms with default ffmpeg:
- on iOS the ffmpeg backend hasn't been tested for a long time and
  we don't have any CI build QtMM + ffmpeg.
- for Linux Yocto builds the gstreamer backend has been set default
  due to hw acceleration issues.

Currently, the documentation says about some hw acceleration issues
with ffmpeg on linux, I'm going to add a separate description
of this later.

Change-Id: I8eb1f04f06fb5edc22dbd455d3ea1a83cefa2ede
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Lars Knoll <lars@knoll.priv.no>
(cherry picked from commit 65465baf906cbb7ad4492e363e643ad7724ff178)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/src/multimedia/doc/src/qtmultimedia-index.qdoc b/src/multimedia/doc/src/qtmultimedia-index.qdoc
index 0d7a3f40a..27f4b7cb5 100644
--- a/src/multimedia/doc/src/qtmultimedia-index.qdoc
+++ b/src/multimedia/doc/src/qtmultimedia-index.qdoc
@@ -164,8 +164,8 @@
     On most platforms, there are two different backends that can be used for Qt Multimedia.
 
     In Qt 6.5, we're setting \l {http://ffmpeg.org}{FFmpeg framework} as the default backend on
-    Windows, Linux, macOS/iOS, and Android. Native backends, namely gstreamer on Linux,
-    AVFoundation on macOS/iOS, WMF on Windows, and the MediaCodec framework on Android,
+    Windows, macOS, Android, and Linux except Yocto distribution. Native backends, namely gstreamer on Linux,
+    AVFoundation on macOS, WMF on Windows, and the MediaCodec framework on Android,
     were the default in 6.4. These are still available but with limited support.
     This means that we will strive to fix critical issues with the native backends, but don't
     guarantee fixing minor issues and won't implement new features with native backends.
@@ -174,13 +174,13 @@
 
     We aim to align the behavior on all the platforms, especially, with the ffmpeg backend.
     Despite this fact we still have platform-dependent issues with formats, codecs, advanced camera
-    features, and screen capturing. This happens since we use some platform API anyway,
-    even with ffmpeg, and there are specific problems with ffmpeg hardware acceleration.
+    features, and screen capturing. This happens since we use some platform API anyway, even with ffmpeg,
+    and there are specific problems with ffmpeg hardware acceleration, mostly on Linux run on ARM architectures.
     Known backend-dependent limitations will be documented in the respective classes and methods.
 
     In the case of issues with the default ffmpeg backend, we suggest testing with a native backend.
     You can switch to native backends by setting the \c{QT_MEDIA_BACKEND} environment variable
-    to \c windows, \c gstreamer (on Linux), \c darwin (on macOS/iOS), or \c android:
+    to \c windows, \c gstreamer (on Linux), \c darwin (on macOS), or \c android:
 
     \code
     export QT_MEDIA_BACKEND=darwin
@@ -192,6 +192,8 @@
     export QT_MEDIA_BACKEND=ffmpeg
     \endcode
 
+    On the Qt Multimedia compilation stage the default media backend can be configured
+    via cmake variable \c{QT_DEFAULT_MEDIA_BACKEND}.
 
     \list
       \li \l{Qt Multimedia on macOS and iOS}{macOS and iOS}