Instead of recreating a first pass stat file for the next renditions, you can use the previous simply launching the second passes of the next renditionsįfmpeg –i IN –pass 2 –an –vcodec libx264 –r 30 –b 1000k –bufsize 1000k –keyint_min 60 –g 120 –s 854×480 –vpre slower O_1000.mp4įfmpeg –i IN –pass 2 –an –vcodec libx264 –r 30 –b 500k –bufsize 500k –keyint_min 60 –g 120 –s 640×360 –vpre slower O_500.mp4 The first pass generates a stat file for the second pass.įfmpeg –i IN –pass 2 –an –vcodec libx264 –r 30 –b 1500k –bufsize 1500k –keyint_min 60 –g 120 –s 1280×720 –vpre slower OUT_1500.mp4 This command line is the first pass of the first rendition. You know that encoding for dynamic streaming techniques (HDS, HLS, Silverlight) requires the renditions to have aligned keyframes and be CBR or capped VBR.Ī neat trick to avoid the limit of fixed length GOPs is to assure a consistent alignment of keyframes across renditions reusing the same first pass statfile across renditions.įfmpeg –i IN –pass 1 –an –vcodec libx264 –r 30 –b 1500k –bufsize 1500k –keyint_min 60 –g 120 –s 1280×720 –vpre slower_fastfirstpass OUT_1500.mp4 Optimize multi-pass multi-bitrates encoding This article will be enriched in the next weeks and months to include even more advanced examples and use cases that can be solved with a smart use of FFmpeg. This fifth article wants to add more advanced use cases and usages to what was presented and discussed in the previous 4 parts. Not for everyone but very useful when you want the control and performance of x264 and all the input and output options of FFmpeg. Last but not least, FFmpeg introduced the possibility to control directly the parameters of x264lib using the -x264opts command. Read point 2 below to know about alternatives. Take a look at the updates of PART II to have more informations about new syntax and obsolete parameters.Īnother important change is realated to libfaac library which is now external.
In case of multiple AV tracks there also an optiona parameter to specify the track number.
The most important changes are around parameters like -vcodec, -b, -ab, -vframes, etc… to avoid misunderstandings now a stream_identifier has been added to specify if the parameter is related to the audio or video track. Above you find the Index of the articles.
So this is also a good opportunity for you to refresh your knowledge about FFmpeg and the current state-of-the-art. In this year a lot of things happened on the FFmpeg side (and not only), so I have corrected a lot of small errors and changes in syntax of commonly used commands. PART IV – FFmpeg for streaming (revised 0)Īfter almost one year from the starting post of this series dedicated to FFmpeg I have found some time to catch-up with this topic and revise/refresh the series. PART II – Parameters and recipes (revised 0)
0 kommentar(er)
