Add Video4Linux codecs (decoder) support

- tested on a Pi3 (H264, MPEG4, MPEG2) but should get some hardware
decoding working on other SoCs
- only 'copy back' support at present. DRM PRIME support may be added
for copy free rendering - and hopefully improved performance
- the main problem  in testing is that the Pi3 VC4 drivers do not return
any interlacing flags (kernel source tree checked) - so interlacing is
not autodetected.
- there is some static initialisation to ensure the v4l2-dec decoder
isn't available where not supported - but the check may need
improvement.
- HEVC not tested (no Pi4 here) or indeed the VC6 drivers
- requires the open source Pi drivers to be enabled.

mythtv/configure

@@ -2598,7 +2598,7 @@ opengl_deps_any="agl_h GL_gl_h EGL_egl_h GLES2_gl2_h darwin windows x11"
 opengles_deps="GLES2_gl2_h"
 opengl_video_deps="opengl"
 opengl_themepainter_deps="opengl"
-v4l2_deps="backend linux_videodev2_h"
+v4l2_deps="linux_videodev2_h"
 v4l1_deps="backend v4l2 linux_videodev_h"
 xrandr_deps="x11"
 asi_deps="backend"
@@ -7352,6 +7352,7 @@ if enabled x11 ; then
   echo "VAAPI support             ${vaapi-no}"
   echo "NVDEC support             ${nvdec-no}"
 fi
+  echo "Video4Linux codecs        ${v4l2-no}"
   echo "OpenGL support            ${opengl-no}"
   echo "OpenGL video              ${opengl_video-no}"
   echo "OpenGL ThemePainter       ${opengl_themepainter-no}"

mythtv/libs/libmythtv/decoders/avformatdecoder.cpp

@@ -71,6 +71,10 @@ extern "C" {
 #include "mythvdpauhelper.h"
 #endif
 
+#ifdef USING_V4L2
+#include "mythv4l2m2mcontext.h"
+#endif
+
 extern "C" {
 #include "libavutil/avutil.h"
 #include "libavutil/error.h"
@@ -389,6 +393,14 @@ void AvFormatDecoder::GetDecoders(render_opts &opts)
     (*opts.equiv_decoders)["vtb"].append("dummy");
     (*opts.equiv_decoders)["vtb-dec"].append("dummy");
 #endif
+#ifdef USING_V4L2
+    if (MythV4L2M2MContext::HaveV4L2Codecs())
+    {
+        opts.decoders->append("v4l2-dec");
+        (*opts.equiv_decoders)["v4l2-dec"].append("dummy");
+    }
+#endif
+
     PrivateDecoder::GetDecoders(opts);
 }
 
@@ -1580,6 +1592,13 @@ void AvFormatDecoder::InitVideoCodec(AVStream *stream, AVCodecContext *enc,
         m_directrendering = false;
     }
     else
+#endif
+#ifdef USING_V4L2
+    if (codec_is_v4l2_dec(m_video_codec_id))
+    {
+        m_directrendering = false;
+    }
+    else
 #endif
     if (codec1 && codec1->capabilities & AV_CODEC_CAP_DR1)
     {
@@ -2404,7 +2423,7 @@ int AvFormatDecoder::ScanStreams(bool novideo)
             }
 
             m_video_codec_id = kCodec_NONE;
-            int version = mpeg_version(enc->codec_id);
+            uint version = mpeg_version(enc->codec_id);
             if (version)
                 m_video_codec_id = static_cast<MythCodecID>(kCodec_MPEG1 + version - 1);
 
@@ -2520,6 +2539,24 @@ int AvFormatDecoder::ScanStreams(bool novideo)
                     }
                 }
 #endif // USING_NVDEC
+#ifdef USING_V4L2
+                if (!foundgpudecoder)
+                {
+                    MythCodecID v4l2mcid;
+                    AVPixelFormat pix_fmt = AV_PIX_FMT_YUV420P;
+                    v4l2mcid = MythV4L2M2MContext::GetSupportedCodec(enc, &codec, dec,
+                                    mpeg_version(static_cast<int>(enc->codec_id)), pix_fmt);
+
+                    if (codec_is_v4l2_dec(v4l2mcid))
+                    {
+                        gCodecMap->freeCodecContext(m_ic->streams[selTrack]);
+                        enc = gCodecMap->getCodecContext(m_ic->streams[selTrack], codec);
+                        m_video_codec_id = v4l2mcid;
+                        enc->pix_fmt = pix_fmt;
+                        foundgpudecoder = true;
+                    }
+                }
+#endif // USING_V4L2
             }
             // default to mpeg2
             if (m_video_codec_id == kCodec_NONE)

mythtv/libs/libmythtv/decoders/mythcodeccontext.cpp

@@ -43,6 +43,10 @@
 #ifdef USING_MEDIACODEC
 #include "mythmediacodeccontext.h"
 #endif
+#ifdef USING_V4L2
+#include "mythv4l2m2mcontext.h"
+#endif
+
 #include "mythcodeccontext.h"
 
 #define LOC QString("MythCodecContext: ")
@@ -77,6 +81,11 @@ MythCodecContext *MythCodecContext::CreateContext(DecoderBase *Parent, MythCodec
     if (codec_is_mediacodec(Codec) || codec_is_mediacodec_dec(Codec))
         mctx = new MythMediaCodecContext(Parent, Codec);
 #endif
+#ifdef USING_V4L2
+    if (codec_is_v4l2_dec(Codec))
+        mctx = new MythV4L2M2MContext(Parent, Codec);
+#endif
+
     Q_UNUSED(Codec);
 
     if (!mctx)

mythtv/libs/libmythtv/libmythtv.pro

@@ -662,6 +662,8 @@ using_backend {
         HEADERS += recorders/v4l2encsignalmonitor.h
         SOURCES += recorders/v4l2encsignalmonitor.cpp
 
+        HEADERS += mythv4l2m2mcontext.h
+        SOURCES += mythv4l2m2mcontext.cpp
         DEFINES += USING_V4L2
     }
 

mythtv/libs/libmythtv/mythcodecid.cpp

@@ -367,7 +367,7 @@ AVCodecID myth2av_codecid(MythCodecID codec_id, bool &vdpau)
     return AV_CODEC_ID_NONE;
 }
 
-int mpeg_version(int codec_id)
+uint mpeg_version(int codec_id)
 {
     switch (codec_id)
     {

mythtv/libs/libmythtv/mythcodecid.h

@@ -292,7 +292,7 @@ inline AVCodecID myth2av_codecid(MythCodecID codec_id)
 }
 
 // AV codec id convenience functions
-int mpeg_version(int codec_id);
+uint mpeg_version(int codec_id);
 #define CODEC_IS_H264(id)     (mpeg_version(id) == 5)
 #define CODEC_IS_MPEG(id)     (mpeg_version(id) && mpeg_version(id) <= 2)
 #define CODEC_IS_FFMPEG_MPEG(id) (CODEC_IS_MPEG(id))

mythtv/libs/libmythtv/mythframe.h

@@ -484,6 +484,12 @@ static inline void copyplane(uint8_t* dst, int dst_pitch,
                              const uint8_t* src, int src_pitch,
                              int width, int height)
 {
+    if ((dst_pitch == width) && (src_pitch == width))
+    {
+        memcpy(dst, src, static_cast<size_t>(width * height));
+        return;
+    }
+
     for (int y = 0; y < height; y++)
     {
         memcpy(dst, src, static_cast<size_t>(width));