Yuv420p is a common 8-bit and yuv420p10le a 10-bit pixel format. Most of the non-FFmpeg-based players cannot decode H.264 files holding lossless content. The range of the scale for crf and qp for 8-bit is from 0 to 51, where 0 is lossless, approximately 18 is “visually lossless”, 23 is the default value and 51 is worst possible. You can use the parameter -qp 18 (quantisation parameter) rather than -crf 18 (constant rate factor) which gives a similar “visually lossless” result. Slower encoding means that more time is needed, but the compression rate is better. Possible -preset values for the H.264 codec include veryslow, slow, medium, fast and veryfast. If the source should be RGB, then you might choose the video codec libx264rgb rather than libx264. The video codec is specified by -codec:video, which may be abbreviated as -c:v (or -codec:v or -c:video). c:a copy re-encodes the audio stream using the same audio codec output_file path, name and extension of the output file Discussion pix_fmt yuv420p The pixel format for “YUV” colour space with 4:2:0 chroma subsampling and planar colour alignment is chosen for best compatibility.
crf constant_rate_factor A parameter of 18 means a “visually lossless” compression. preset preset_value A slower encoding preset means a better compression rate. c:a copy \ output_file Command syntax ffmpeg starts the command -i input_file path, name and extension of the input file -c:v libx264 The library libx264 re-encodes the video stream using the H.264 video codec. c:a copy \ output_file Generic command ffmpeg \ The reset default to medium and don’t play on an iPad or iPhone.Transcode a video file by using the H.264 codec for dissemination purposes. I’ve tried all of the provided presets, most produce super huge files and no video. I do the transcode like this: -vcodec libx264 -vpreset preset/libx264-ipod640.ffpreset rtmp:///vod/dvrTest2 file://Users/myHomedir/tmp/dvrTest2.mp4Īnd get the following from libx264 20:44:06.866 ERROR org.ffmpeg - Default settings detected, using medium profile I’m using Xuggler - not ffmpeg directly, but the latest version supports preset files. Here’s the output from the Wowza log: INFO server comment - MediaReaderH264Cupertino.handlePacket: AAC Audio info: Problem is, the files generated are at level 5.1 and most iPhones and many iPads require 3.0 to play. I’ve been able to generate H.264/AAC files that play beautifully on my desktop over Wowza 2.X or 3.0 pre-release from an FLV stream generated by FlashPlayer.
This ought to be on the Xuggler boards, but I’m still waiting to get permission to post…
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