rpi: add --hwdec=rpi-copy

This means it can be used with normal video filters.

Might help out with #3604.

DOCS/man/options.rst

@@ -622,6 +622,7 @@ Video
     :d3d11va-copy: copies video back to system RAM (Windows only)
     :mediacodec: copies video back to system RAM (Android only)
     :rpi:       requires ``--vo=opengl`` (Raspberry Pi only - default if available)
+    :rpi-copy:  copies video back to system RAM (Raspberry Pi only)
     :cuda:      requires ``--vo=opengl`` (Any platform CUDA is available)
     :cuda-copy: copies video back to system RAM (Any platform CUDA is available)
 
@@ -707,6 +708,9 @@ Video
         to deinterlace inside the decoder. However, traditional deinterlacing
         filters can be used in this case.
 
+        ``rpi`` always uses the hardware overlay renderer, even with
+        ``--vo=opengl``.
+
         All other methods, in particular the copy-back methods (like
         ``dxva2-copy`` etc.) are either fully safe, or not worse than software
         decoding.

options/options.c

@@ -98,6 +98,7 @@ const struct m_opt_choice_alternatives mp_hwdec_names[] = {
     {"d3d11va",     HWDEC_D3D11VA},
     {"d3d11va-copy",HWDEC_D3D11VA_COPY},
     {"rpi",         HWDEC_RPI},
+    {"rpi-copy",    HWDEC_RPI_COPY},
     {"mediacodec",  HWDEC_MEDIACODEC},
     {"cuda",        HWDEC_CUDA},
     {"cuda-copy",   HWDEC_CUDA_COPY},

video/decode/vd_lavc.c

@@ -141,6 +141,11 @@ static const struct vd_lavc_hwdec mp_vd_lavc_rpi = {
     .lavc_suffix = "_mmal",
     .image_format = IMGFMT_MMAL,
 };
+static const struct vd_lavc_hwdec mp_vd_lavc_rpi_copy = {
+    .type = HWDEC_RPI_COPY,
+    .lavc_suffix = "_mmal",
+    .copying = true,
+};
 #endif
 
 #if HAVE_ANDROID
@@ -162,6 +167,7 @@ static const struct vd_lavc_hwdec mp_vd_lavc_cuda_copy = {
 static const struct vd_lavc_hwdec *const hwdec_list[] = {
 #if HAVE_RPI
     &mp_vd_lavc_rpi,
+    &mp_vd_lavc_rpi_copy,
 #endif
 #if HAVE_VDPAU_HWACCEL
     &mp_vd_lavc_vdpau,

video/hwdec.h

@@ -20,6 +20,7 @@ enum hwdec_type {
     HWDEC_D3D11VA,
     HWDEC_D3D11VA_COPY,
     HWDEC_RPI,
+    HWDEC_RPI_COPY,
     HWDEC_MEDIACODEC,
     HWDEC_CUDA,
     HWDEC_CUDA_COPY,