It is customary for RTP streams to use two ports with an open port between them. The -flags global_header is used to force ffmpeg to spit out some important audio specifications in the SDP it generates (you use an SDP file on the Wowza server to connect the RTMP stream to the RTP stream Wowza needs to know all about the audio and video to interpret it properly).Īgain, we specify the rtp format with the -f option, and we provide a URL. First, we use the -vn option to indicate that this output does not contain video. Without deinterlacing, you can see some very unpleasant “comb” artifacts in your digitized video.Īgain, this is very similar to the options we provided for our MPEG4 output, with some notable differences. ffmpeg will try to keep the video close to the desired bitrate, and the tolerance tells it how much leeway it has above and below the target bitrate.įinally, we are deinterlacing the video, as the source was NTSC interlaced video. The -s option specifies our frame size, the -b option specifies the desired bitrate, and the -bt option is the bitrate tolerance. It also will have a detrimental effect on file size. With a smaller number, your output will have more keyframes, which means that streaming clients will be able to recover more quickly if they drop packets for some reason. The -g option is the “group of pictures” (GOP) size, which is the number of frames between keyframes. The -r option specifies that our output will be 20 frames per second. We are going to crop our video a few pixels around the border, as we were getting some noise around the edges of our source video. The -threads 0 option instructs ffmpeg to use the optimal number of threads when encoding. I have not seen this documented very well. The first is quality, and the second is the profile to use (main, baseline, etc., with “main” being the default). The -vpre option means that we will use the default quality preset (note that when using libx264 to encode, you can specify two -vpre options. We’re going to use H.264 compression, as provided by the libx264 library. Here we are specifying our video output options. croptop 6 -cropbottom 6 -cropleft 9 -cropright 9 \ vcodec libx264 -vpre default -threads 0 \ acodec libfaac -ac 2 -ab 192k -ar 44100 \
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