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• Using lcov With FFmpeg/Libav

  21 novembre 2011, par Multimedia Mike — Programming, code coverage, ffmpeg, lcov, libav

  Last year, I delved into code coverage tools and their usage with FFmpeg. I learned about using GNU gcov, which is powerful but pretty raw about the details it provides to you. I wrote a script to help interpret its output and later found another script called gcovr to do the same, only much better.

  I later found another tool called lcov which is absolutely amazing for understanding code coverage of your software. I’ve been meaning to use it to further FATE test coverage for the multimedia projects.

  
  
  Click for larger image
  

  Basic Instructions
  Install the lcov tool, of course. In Ubuntu, 'apt-get install lcov' will do the trick.

  Build the project with code coverage support, i.e.,

  ./configure —enable-gpl —samples=/path/to/fate/samples \
   —extra-cflags="-fprofile-arcs -ftest-coverage" \
   —extra-ldflags="-fprofile-arcs -ftest-coverage"
  make
  

  Clear the coverage data :

  lcov —directory . —zerocounters
  

  Run the software (in this case, the FATE test suite) :

  make fate
  

  Let lcov work its magic :

  lcov —directory . —capture —output-file coverage.info
  mkdir html-output
  genhtml -o html-output coverage.info
  

  At this point, you can aim your web browser at html-output/index.html to learn everything you could possibly want to know about code coverage of the test suite. You can sort various columns in order to see which modules have the least code coverage. You can drill into individual source files and see highlighted markup demonstrating which lines have been executed.

  As you can see from the screenshot above, FFmpeg / Libav are not anywhere close to full coverage. But lcov provides an exquisite roadmap.

• Use FFMPEG to create video from jpeg, and index using vlc

  16 novembre 2011, par Greg

  OpenSuse 11.4
  FFMEG 0.8.5

  I'm using FFMPEG to create a 5 minute mpeg from about 2100 individual jpegs (7fps). I've been using the following command (OpenSuse 11.4)
  /usr/bin/ffmpeg -y -r 7.01 -i %03d-capture.jpg -s 800x600 -r 25 Event-3692-r1-s1-3.mpg

  Now I Try to open the file (In windows XP with VLC 1.1.11 Player).
  Media->AdvancedFileOpen
  *I select "Show more options" and set StartTime to 5s. I expect that the video should start 5 seconds in, but instead it starts at a seemingling random (although consistent) time of 30 seconds in.

  I also tried changing ffmpeg command to :
  /usr/bin/ffmpeg -sameq -y -r 7.01 -i %03d-capture.jpg -s 800x600 -r 25 Event-3692-r1-s1-3.mpg
  *This result in about a constant 2x offset (5sec => 10sec) (10s => 20s) etc. But filesize is also about 6x larger, which is a strain on my storage.

  I also tried
  /usr/bin/ffmpeg -y -r 7.01 -i %03d-capture.jpg -s 800x600 -r 25 -f mpegts Event-3692-r1-s1-3.mpg
  *This result in vlc not indexing at all into my video. Also not desired. Anybody have any clues what is going on here. It is very important for me to be able to use this VLC feature and have it work correctly.

  Thanks in advance

• VP9 encoding using FFmpeg [migrated]

  20 mai 2013, par Computer_Engineer

  I want to ask if ffmpeg supports VP9 encoding, and if not : how can I encode VP9 videos ?
  I try using the command :

  ./ffmpeg-vp9 -y -i /home/mc/test.mkv -t 00:00:30 -c:v libvpx-vp9 -strict -2 -quality good -b:v 600k -speed 16 -rc_lookahead 25 -pass 1 2.webm

  but it shows an error in splitting the command appeared (for vp9).