added CRF and updated docs

Author: berndpfrommer

README.md

@@ -57,23 +57,28 @@ export LD_LIBRARY_PATH=/home/foo/ffmpeg/build/lib:${LD_LIBRARY_PATH}
 ### How to use ffmpeg hardware accelerated encoding on the NVidia Jetson
 
 Follow the instructions
-[here](https://github.com/jocover/jetson-ffmpeg) to build a version of
-ffmpeg that supports NVMPI. Then follow the section above on how to
+[here](https://github.com/Keylost/jetson-ffmpeg) to build a version of
+ffmpeg that supports NVMPI. This long magic line should build a nvmpi enabled
+version of ffmpeg and install it under ``/usr/local/``:
+```
+git clone https://github.com/berndpfrommer/jetson-ffmpeg.git && cd jetson-ffmpeg && mkdir build && cd build && cmake -DCMAKE_INSTALL
+_PREFIX:PATH=/usr/local .. && make install && ldconfig && cd ../.. && git clone git://source.ffmpeg.org/ffmpeg.git -b release/7.1 --
+depth=1 &&cd jetson-ffmpeg && ./ffpatch.sh ../ffmpeg && cd ../ffmpeg && ./configure --enable-nvmpi --enable-shared --disable-static 
+--prefix=/usr/local && make install
+```
+
+Then follow the section above on how to
 actually use that custom ffmpeg library. As always first test on the
 CLI that the newly compiled ``ffmpeg`` command now supports
-``h264_nvmpi``. Afterwards you should be able to use e.g. the ``ffmpeg_image_transport`` with
-parameters like so:
-
-The transport can now be configured to use nvmpi like so:
+``h264_nvmpi``. The transport can then be configured to use
+nvmpi like so:
 
 ```
         parameters=[{'ffmpeg_image_transport.encoding': 'h264_nvmpi',
                      'ffmpeg_image_transport.profile': 'main',
                      'ffmpeg_image_transport.preset': 'll',
-                     'ffmpeg_image_transport.gop': 15}]
+                     'ffmpeg_image_transport.gop_size': 15}]
 ```
-
-
 ## License
 
 This software is issued under the Apache License Version 2.0.

include/ffmpeg_encoder_decoder/encoder.hpp

@@ -80,7 +80,11 @@ class Encoder
     Lock lock(mutex_);
     delay_ = p;
   }
-
+  void setCRF(const std::string & c)
+  {
+    Lock lock(mutex_);
+    crf_ = c;
+  }
   void setQMax(int q)
   {
     Lock lock(mutex_);
@@ -152,6 +156,7 @@ class Encoder
   std::string profile_;  // e.g. "main", "high", "rext"
   std::string tune_;     // e.g. "tune"
   std::string delay_;    // default is 4 frames for parallel processing. 0 is lowest latency
+  std::string crf_;      // constant rate factor. 0 is lossless, 51 is worst quality
   int qmax_{0};          // max allowed quantization. The lower the better quality
   int GOPSize_{15};      // distance between two keyframes
   AVPixelFormat pixFormat_{AV_PIX_FMT_NONE};

src/encoder.cpp

@@ -207,6 +207,7 @@ void Encoder::doOpenCodec(int width, int height)
   setAVOption("preset", preset_);
   setAVOption("tune", tune_);
   setAVOption("delay", delay_);
+  setAVOption("crf", crf_);
   RCLCPP_DEBUG(
     logger_,
     "codec: %10s, profile: %10s, preset: %10s,"