The H.264 name follows the ITU-T naming convention, where Recommendations are given a letter corresponding to their series and a recommendation number within the series. H.264 is part of "H-Series Recommendations: Audiovisual and multimedia systems". H.264 is further categorized into "H.200-H.499: Infrastructure of audiovisual services" and "H.260-H.279: Coding of moving video".[10] The MPEG-4 AVC name relates to the naming convention in ISO/IEC MPEG, where the standard is part 10 of ISO/IEC 14496, which is the suite of standards known as MPEG-4. The standard was developed jointly in a partnership of VCEG and MPEG, after earlier development work in the ITU-T as a VCEG project called H.26L. It is thus common to refer to the standard with names such as H.264/AVC, AVC/H.264, H.264/MPEG-4 AVC, or MPEG-4/H.264 AVC, to emphasize the common heritage. Occasionally, it is also referred to as "the JVT codec", in reference to the Joint Video Team (JVT) organization that developed it. (Such partnership and multiple naming is not uncommon. For example, the video compression standard known as MPEG-2 also arose from the partnership between MPEG and the ITU-T, where MPEG-2 video is known to the ITU-T community as H.262.[11]) Some software programs (such as VLC media player) internally identify this standard as AVC1.
Like other ISO/IEC MPEG video standards, H.264/AVC has a reference software implementation that can be freely downloaded.[50] Its main purpose is to give examples of H.264/AVC features, rather than being a useful application per se. Some reference hardware design work has also been conducted in the Moving Picture Experts Group.The above-mentioned aspects include features in all profiles of H.264. A profile for a codec is a set of features of that codec identified to meet a certain set of specifications of intended applications. This means that many of the features listed are not supported in some profiles. Various profiles of H.264/AVC are discussed in next section.
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Encoded packets are then passed to the decoder (unless streamcopy is selectedfor the stream, see further for a description). The decoder producesuncompressed frames (raw video/PCM audio/...) which can be processed further byfiltering (see next section). After filtering, the frames are passed to theencoder, which encodes them and outputs encoded packets. Finally those arepassed to the muxer, which writes the encoded packets to the output file.
For the third output, codec option for audio streams has been setto copy, so no decoding-filtering-encoding operations will occur, or can occur.Packets of selected streams shall be conveyed from the input file and muxed within the outputfile.
A stream specifier is a string generally appended to the option name andseparated from it by a colon. E.g. -codec:a:1 ac3 contains thea:1 stream specifier, which matches the second audio stream. Therefore, itwould select the ac3 codec for the second audio stream.
In the above example, a multichannel audio stream is mapped twice for output.The first instance is encoded with codec ac3 and bitrate 640k.The second instance is downmixed to 2 channels and encoded with codec aac. A bitrate of 128k is specified for it usingabsolute index of the output stream.
Use fixed quality scale (VBR). The meaning of q/qscale iscodec-dependent.If qscale is used without a stream_specifier then it applies onlyto the video stream, this is to maintain compatibility with previous behaviorand as specifying the same codec specific value to 2 different codecs that isaudio and video generally is not what is intended when no stream_specifier isused.
-enc_stats_pre writes information about raw video or audio frames rightbefore they are sent for encoding, while -enc_stats_post writesinformation about encoded packets as they are received from the encoder. Everyframe or packet produces one line in the specified file. The format of this lineis controlled by -enc_stats_pre_fmt / -enc_stats_post_fmt.
This is a typical DVD ripping example; the input is a VOB file, theoutput an AVI file with MPEG-4 video and MP3 audio. Note that in thiscommand we use B-frames so the MPEG-4 stream is DivX5 compatible, andGOP size is 300 which means one intra frame every 10 seconds for 29.97fpsinput video. Furthermore, the audio stream is MP3-encoded so you needto enable LAME support by passing --enable-libmp3lame to configure.The mapping is particularly useful for DVD transcodingto get the desired audio language.
libcelt allows libavcodec to decode the Xiph CELT ultra-low delay audio codec.Requires the presence of the libcelt headers and library during configuration.You need to explicitly configure the build with --enable-libcelt.
libgsm allows libavcodec to decode the GSM full rate audio codec. Requiresthe presence of the libgsm headers and library during configuration. You needto explicitly configure the build with --enable-libgsm.
libilbc allows libavcodec to decode the Internet Low Bitrate Codec (iLBC)audio codec. Requires the presence of the libilbc headers and library duringconfiguration. You need to explicitly configure the build with--enable-libilbc.
libopencore-amrnb allows libavcodec to decode the Adaptive Multi-RateNarrowband audio codec. Using it requires the presence of thelibopencore-amrnb headers and library during configuration. You need toexplicitly configure the build with --enable-libopencore-amrnb.
libopencore-amrwb allows libavcodec to decode the Adaptive Multi-RateWideband audio codec. Using it requires the presence of thelibopencore-amrwb headers and library during configuration. You need toexplicitly configure the build with --enable-libopencore-amrwb.
Dolby Surround Mode. Specifies whether the stereo signal uses Dolby Surround(Pro Logic). This field will only be written to the bitstream if the audiostream is stereo. Using this option does NOT mean the encoder will actuallyapply Dolby Surround processing.
Set noise floor bias for impulse blocks. The value is a float number from-15.0 to 0.0. A negative bias instructs the encoder to pay special attentionto the crispness of transients in the encoded audio. The tradeoff for bettertransient response is a higher bitrate.
This provides wrappers to encoders (both audio and video) in theMediaFoundation framework. It can access both SW and HW encoders.Video encoders can take input in either of nv12 or yuv420p form(some encoders support both, some support only either - in practice,nv12 is the safer choice, especially among HW encoders).
You can select the output format of each frame with ffmpeg byspecifying the audio and video codec and format. For example tocompute the CRC of the input audio converted to PCM unsigned 8-bitand the input video converted to MPEG-2 video, use the command:
With ffmpeg, you can select the output format to which theaudio and video frames are encoded before computing the CRC for eachpacket by specifying the audio and video codec. For example, tocompute the CRC of each decoded input audio frame converted to PCMunsigned 8-bit and of each decoded input video frame converted toMPEG-2 video, use the command:
By default audio frames are converted to signed 16-bit raw audio andvideo frames to raw video before computing the hash, but the outputof explicit conversions to other codecs can also be used. It uses theSHA-256 cryptographic hash function by default, but supports severalother algorithms.
By default audio frames are converted to signed 16-bit raw audio andvideo frames to raw video before computing the hash, but the outputof explicit conversions to other codecs can also be used. Timestampsare ignored. It uses the SHA-256 cryptographic hash function by default,but supports several other algorithms.
It is different from specifying several outputs to the ffmpegcommand-line tool. With the tee muxer, the audio and video data will be encoded only once.With conventional multiple outputs, multiple encoding operations in parallel are initiated,which can be a very expensive process. The tee muxer is not useful when using the libavformat APIdirectly because it is then possible to feed the same packets to several muxers directly.
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High Efficiency Video Coding (HEVC) or also called H.265 is a new video codec and new generation video compression standard. It doubles the data compression ratio compared to H.264 or MPEG-4 AVC at the same level of video quality. This H.265/HEVC also can support 4K and 8K Ultra High Definition video, with a picture size up to 81924320 pixels. Hence, it is recommended to encode H.264/AVC MP4 to H.265/HEVC MP4 if you want to gain smaller file size or play high quality video over a cellular network.
With it, you are able to encode MP4 as well as MKV, MTS, AVI, WMV, MOV, MPEG, etc. to H.265 MP4 rapidly in high quality with several mouse clicks. What's more, it also supports ripping Blu-ray, DVD to H.265 MP4 video without quality loss. Aside from encode movies to H.265, it also can decode H.265 to other video format, or extract audio from H.265 and then convert to audio format. With the Edit function, you can trim, crop, add watermark, adjust effects, add subtitles as you like. If you are going to encode H.264 MP4 to H.265 on Mac OS X (El Capitan and Yosemite included), you can get iFastime Video Converter Ultimate for Mac. Download it from below and read further to know how to successfully convert H.264 MP4 video files into H.265 MP4 format. 2ff7e9595c
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