AvFormatDecoder: Pass optional AVDictionary options to avcodec_open2

- used to reduce the number of v4l2_m2m capture buffers
MythTV · Jul 10, 2019 · 5162cc0 · 5162cc0
1 parent eba8bab
commit 5162cc0
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Showing 5 changed files with 22 additions and 6 deletions.
diff --git a/mythtv/libs/libmythtv/decoders/avformatdecoder.cpp b/mythtv/libs/libmythtv/decoders/avformatdecoder.cpp
@@ -2601,16 +2601,17 @@ int AvFormatDecoder::ScanStreams(bool novideo)
                 QString("Using %1 for video decoding")
                 .arg(GetCodecDecoderName()));
 
+            AVDictionary *options = m_mythcodecctx->GetDecoderOptions();
             {
                 QMutexLocker locker(avcodeclock);
-
-                if (!OpenAVCodec(enc, codec))
+                if (!OpenAVCodec(enc, codec, options))
                 {
+                    av_dict_free(&options);
                     scanerror = -1;
                     break;
                 }
             }
-
+            av_dict_free(&options);
             break;
         }
     }
@@ -2673,15 +2674,16 @@ int AvFormatDecoder::ScanStreams(bool novideo)
     return scanerror;
 }
 
-bool AvFormatDecoder::OpenAVCodec(AVCodecContext *avctx, const AVCodec *codec)
+bool AvFormatDecoder::OpenAVCodec(AVCodecContext *avctx, const AVCodec *codec,
+                                  AVDictionary *Options)
 {
     QMutexLocker locker(avcodeclock);
 
 #ifdef USING_MEDIACODEC
     if (QString("mediacodec") == codec->wrapper_name)
         av_jni_set_java_vm(QAndroidJniEnvironment::javaVM(), nullptr);
 #endif
-    int ret = avcodec_open2(avctx, codec, nullptr);
+    int ret = avcodec_open2(avctx, codec, &Options);
     if (ret < 0)
     {
         char error[AV_ERROR_MAX_STRING_SIZE];

diff --git a/mythtv/libs/libmythtv/decoders/avformatdecoder.h b/mythtv/libs/libmythtv/decoders/avformatdecoder.h
@@ -261,7 +261,7 @@ class AvFormatDecoder : public DecoderBase
     bool HasVideo(const AVFormatContext *ic);
     float normalized_fps(AVStream *stream, AVCodecContext *enc);
     void av_update_stream_timings_video(AVFormatContext *ic);
-    bool OpenAVCodec(AVCodecContext *avctx, const AVCodec *codec);
+    bool OpenAVCodec(AVCodecContext *avctx, const AVCodec *codec, AVDictionary *Options = nullptr);
 
     void UpdateFramesPlayed(void) override; // DecoderBase
     bool DoRewindSeek(long long desiredFrame) override; // DecoderBase

diff --git a/mythtv/libs/libmythtv/decoders/mythcodeccontext.h b/mythtv/libs/libmythtv/decoders/mythcodeccontext.h
@@ -67,6 +67,7 @@ class MTV_PUBLIC MythCodecContext
     virtual void   SetDeinterlacing        (AVCodecContext*, VideoDisplayProfile*, bool) {}
     virtual void   PostProcessFrame        (AVCodecContext*, VideoFrame*) {}
     virtual bool   IsDeinterlacing         (bool &, bool = false) { return false; }
+    virtual AVDictionary* GetDecoderOptions(void) { return nullptr; }
 
   protected:
     virtual bool   RetrieveHWFrame         (VideoFrame* Frame, AVFrame* AvFrame);

diff --git a/mythtv/libs/libmythtv/mythv4l2m2mcontext.cpp b/mythtv/libs/libmythtv/mythv4l2m2mcontext.cpp
@@ -83,6 +83,18 @@ bool MythV4L2M2MContext::RetrieveFrame(AVCodecContext *Context, VideoFrame *Fram
     return false;
 }
 
+/*! \brief Reduce the number of capture buffers
+ *
+ * Testing on Pi 3, the default of 20 is too high and leads to memory allocation
+ * failures in the the kernel driver.
+*/
+AVDictionary* MythV4L2M2MContext::GetDecoderOptions(void)
+{
+    AVDictionary *options = nullptr;
+    av_dict_set_int(&options, "num_capture_buffers", 2, 0);
+    return options;
+}
+
 /*! \brief Retrieve a frame from CPU memory
  *
  * This is similar to the default, direct render supporting, get_av_buffer in

diff --git a/mythtv/libs/libmythtv/mythv4l2m2mcontext.h b/mythtv/libs/libmythtv/mythv4l2m2mcontext.h
@@ -14,6 +14,7 @@ class MythV4L2M2MContext : public MythCodecContext
                                           uint            StreamType,
                                           AVPixelFormat  &PixFmt);
     bool        RetrieveFrame            (AVCodecContext *Context, VideoFrame *Frame, AVFrame *AvFrame) override;
+    AVDictionary* GetDecoderOptions      (void) override;
     static bool GetBuffer                (AVCodecContext *Context, VideoFrame *Frame, AVFrame *AvFrame, int);
     static bool GetDRMBuffer             (AVCodecContext *Context, VideoFrame *Frame, AVFrame *AvFrame, int);
     static bool HaveV4L2Codecs           (AVCodecID Codec = AV_CODEC_ID_NONE);