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Mediacoder identi1/11/2024 By default, both parameters have the value ‘0’, which should give optimum results. The latter sets the threshold, known as the beta parameter. The filter automatically determines how strongly (alpha parameter) de-blocking should be applied and in doing so it decides how much of the blocky pattern is unwanted and how much is real. This artefact in source files may be minimised by the De-blocking loop filter, which by default, MediaCoder has enabled for x264 (under the ‘Advanced’ button). Whereas, the increased number of reference frames tends to increase quality, it does require more encoding and, hence, more time.ĭe-blocking: at low bit-rates, video frames tend to break up into macro blocks that form a grid of squares. Typical content could do with 3 to 5 reference frames. Each B-frame needs two reference frames, one before and one after. With a similar function to I-frames, they are used as reference by P- and B-frames. Frames: This is the maximum number of reference frames the encoder can use, presumably, in each GOP group. I did a quick check by setting B-frames to either 0 or 6 and it made no difference to the file size or encoding time (Baseline profile).ħ. Also, even though the 'Baseline' Preset doesn't support B-frames, there is no harm in leaving the B-frame setting at 3, since this merely sets the maximum allowed and the encoder should select the appropriate number (none in this case). By default, MediaCoder sets 3 as the max for B-frames and allows a choice from 1 to 16. However, note that the number of B-frames actually used by x264 probably cannot exceed the number of Ref frames set (below). B-Frames: B-frames are used more efficiently in H264 than in earlier standards, with up to 16 being allowed consecutively, with rarely a problem if 16 is set, since the best number should be auto chosen. Here, the minimum and maximum values are set.Ħ. GOP: the GOP (Group of Pictures) is effectively the number of video frames in the group of frames that begins with each I-frame (Keyframe). Tune: this option allows x264 to optimise things to suit the type of source file. This test was not definitive, but does suggest that the Fast Preset is possibly the most efficient – a good compromise (see Section 3).Ĥ. According to, quality increases rapidly from Ultra-Fast to Very Fast, then, more gradually through Fast and Medium and offers little improvement from Medium through to Placebo. The default in MediaCoder is 'Medium', which is intermediate. They vary from 'Ultra-Fast', for max encoding speed at the expense of quality, to 'Placebo' for maximum quality at the expense of encoding time. Presets: MediaCoder offers 9 choices apart from 'Custom'. Level 4 takes the max bit rate to 20 Mbps and allows 1920x1080 at 30 fps.ģ. Level 3.0 allows up to 10 Mbps for the Baseline and Main profiles and up to 720x576 pixels at 25 fps (PAL) or the equivalent in NTSC (720x480 at 30 fps). For example, Level 2 allows up to 2000 kbps for Baseline to Main and up to 30 fps for up to 352x288. Levels: a level sets restraints on the maximum resolution, frame rate and bit rate, etc. The Main Profile is suitable for Standard Definition TV (720x576 and 720x480), the High is suitable for HD TV and Blu-ray and High10 goes a little further.Ģ. It supports Progressive, not interlaced, as well as I-frames (Keyframes) and P-frames, but not B-frames. Baseline has a minimal implementation for use in low-cost applications, such as video conferencing and mobiles. Apart from Auto, there are Baseline, Main, High and High10. Profiles: MediaCoder offers only 4 of the 17 profiles (sets of capabilities) available for x264. The 7 parameters on the x264 tab are enough to play with! They are discussed below.ġ. A click on this button offers a few more choices and “More Parameters” that opens Settings > Video Encoders > x264 to reveal 70 settings, some of which reflect the user choices already made on the x264 tab. There are 7 options on the tab and there are 3 others that are greyed out (for future extension?) as well as the ‘Advanced’ button. The parameters for achieving the H.264 format are available in MediaCoder on the x264 tab once x264 is set as the Encoder. Also, the Blu-ray disc format includes the H.264/AVC High Profile as one of 3 mandatory video compression formats. For example, it is claimed to give the same Digital Satellite TV quality as current MPEG-2 implementations with less than half the bit rate, for example, MPEG-2 at around 3.5 Mbps is equivalent to H.264 at only 1.5 Mbps. With the use of H.264, bit rate savings of 50% or more have been reported. The H.264 Codec is based on the MPEG-4 standard Part 10 and uses the MPEG-4 AVC profile (Advanced Video Coding), which was designed to give a similar quality to earlier standards, such as MPEG2, H263 and Xvid (MPEG4-Part 2), at substantially smaller bitrates, at maybe ~half the bitrates! However, it requires more computing power.
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