Consequently, assuming the same quality setting (I will use -crf 24), the files should be larger for e.g., faster preset than for the slower preset. So as I understand it, the ffmpeg presets should not affect the quality of the output video, but should only determine the compression ratio / output file size. Current presets in descending order of speed are: ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow, placebo. Consequently, assuming the same quality setting. General usage is to use the slowest preset that you have patience for. Current presets in descending order of speed are: ultrafast, superfast, veryfast, faster, fast, medium, slow, slower, veryslow, placebo. A slower preset will provide better compression (compression is quality per filesize). I am definitely not an FFMPEG expert, but according to this document:Ī preset is a collection of options that will provide a certain encoding speed to compression ratio. In short, this value is the number of previous frames each P-frame can use Even if you just consider the ref value you can see how veryfast could be lower quality. If it helps here is a git diff from slower to veryfast. This means that a slower preset with the same CRF value will improve quality per bitrate, but might make both quality and bitrate higher or lower. Similar question to yours with answers provided by one of the x264 developers: verb3k | Do different presets have an effect on quality when used with | verb3k: yes, but not too | a 0th-order approximation is that they have no | The main reason there's a difference is because the preset affects how x264 itself measures | that is, it uses better, more accurate methods of measuring | obviously, this will affect the definition of what -crf | It's just not too much, so we can mostly ignore | specifically, there are three big things that can affect the definition of | 1) AQ being | jump: ultrafast to | 2) mbtree being | jump: superfast to | 3) psy-rd being | jump: faster to | above fast there are no more big jumps. Here's an excerpt from a discussion on #x264. For example, use -c:v libx264 -crf 23 -maxrate 4M -bufsize 4M to encode at variable bitrate with a target CRF of 23, but limit the output to a maximum of 4 MBit/s.Yes, quality may vary slightly depending on the preset used, but it should not be a significant amount. Use a constant quality target and limit the bitrate only to catch spikes. The higher the buffer size, the higher the allowed bitrate variation. You'll have to adjust the rate and buffer sizes to the context obviously. As a media producer, some of the content I have exported is sent for feedback at the draft stage, others need to be archived with the best quality at the smallest file size and. Use -b:v 3500K -maxrate 3500K -bufsize 1000K, for example. H264 -preset and -crf benchmarking results ( and why use should always use VERYFAST) So I use ffmpeg all the time to convert video production files using command line. Set up a constrained / variable bit rate process for streaming. Unless you absolutely need to achieve a constant rate output, do not use this option. Warning: This might result in low quality for videos that are hard to encode, and it will waste bits. Setting -b:v, -minrate, and -maxrate to the same levels will achieve that, for example for libx264: ffmpeg -i input.mp4 -c:v libx264 -x264-params "nal-hrd=cbr" -b:v 1M -minrate 1M -maxrate 1M -bufsize 2M output.ts
Typically, you cannot achieve a "perfect" constant bitrate, since the encoder will not waste bits. To set up a CBR process, you have to check what the encoder offers. To summarize, you have several options for limiting bitrate: You typically only use this mode for streaming, since the technique will constrain the bit rate in order to not exceed a certain value which would cause the decoder buffer to over- or underflow. The -minrate/ -maxrate/ -bufsize options control that buffer size. This only makes sense for variable bit rate encoding, where instead of using a constant bit rate or constant quality model, the encoder simulates a transmission with a virtual buffer at the decoder. set ratecontrol buffer size (in bits) (from INT_MIN to INT_MAX) Set maximum bitrate tolerance (in bits/s). However, as the documentation indicates, this is only used in conjunction with bufsize: Set minimum bitrate tolerance (in bits/s). minrate specifies a minimum tolerance to be used: set bitrate (in bits/s) (from 0 to INT_MAX) b:v (or -vb, the same) specifies the target average bit rate for the encoder to use: Also, have a look at this article I wrote, which shows the differences between rate control modes in encoders like x264 and x265.
#FFMPEG H264 PRESET FULL#
Please read the documentation for FFmpeg, and run ffmpeg -h full for the list of options.
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