qsvdec: add support for HW_DEVICE_CTX method

This allows user set hw_device_ctx instead of hw_frames_ctx for QSV
decoders, hence we may remove the ad-hoc libmfx setup code from FFmpeg.

"-hwaccel_output_format format" is applied to QSV decoders after
removing the ad-hoc libmfx code. In order to keep compatibility with old
commandlines, the default format is set to AV_PIX_FMT_QSV, but this
behavior will be removed in the future. Please set "-hwaccel_output_format qsv"
explicitly if AV_PIX_FMT_QSV is expected.

The normal device stuff works for QSV decoders now, user may use
"-init_hw_device args" to initialise device and "-hwaccel_device
devicename" to select a device for QSV decoders.

"-qsv_device device" which was added for workarounding device selection
in the ad-hoc libmfx code still works

For example:

$> ffmpeg -init_hw_device qsv=qsv:hw_any,child_device=/dev/dri/card0
-hwaccel qsv -c:v h264_qsv -i input.h264  -f null -

/dev/dri/renderD128 is actually open for h264_qsv decoder in the above
command without this patch. After applying this patch, /dev/dri/card0
is used.

$> ffmpeg -init_hw_device vaapi=va:/dev/dri/card0 -init_hw_device
qsv=hw@va -hwaccel_device hw -hwaccel qsv -c:v h264_qsv -i input.h264
-f null -

device hw of type qsv is not usable in the above command without this
patch. After applying this patch, this command works as expected.

Reviewed-by: Soft Works <softworkz@hotmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/fftools/ffmpeg_hw.c b/fftools/ffmpeg_hw.c
index fc4a5d31d6..6923c4c5a1 100644
--- a/fftools/ffmpeg_hw.c
+++ b/fftools/ffmpeg_hw.c
@@ -339,6 +339,18 @@ int hw_device_setup_for_decode(InputStream *ist)
         } else if (ist->hwaccel_id == HWACCEL_GENERIC) {
             type = ist->hwaccel_device_type;
             dev = hw_device_get_by_type(type);
+
+            // When "-qsv_device device" is used, an internal QSV device named
+            // as "__qsv_device" is created. Another QSV device is created too
+            // if "-init_hw_device qsv=name:device" is used. There are 2 QSV devices
+            // if both "-qsv_device device" and "-init_hw_device qsv=name:device"
+            // are used, hw_device_get_by_type(AV_HWDEVICE_TYPE_QSV) returns NULL.
+            // To keep back-compatibility with the removed ad-hoc libmfx setup code,
+            // call hw_device_get_by_name("__qsv_device") to select the internal QSV
+            // device.
+            if (!dev && type == AV_HWDEVICE_TYPE_QSV)
+                dev = hw_device_get_by_name("__qsv_device");
+
             if (!dev)
                 err = hw_device_init_from_type(type, NULL, &dev);
         } else {