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| .IX Title "FFMPEG-BITSTREAM-FILTERS 1" |
| .TH FFMPEG-BITSTREAM-FILTERS 1 "2013-12-14" " " " " |
| .SH "NAME" |
| ffmpeg\-bitstream\-filters \- FFmpeg bitstream filters |
| .SH "DESCRIPTION" |
| .IX Header "DESCRIPTION" |
| This document describes the bitstream filters provided by the |
| libavcodec library. |
| .PP |
| A bitstream filter operates on the encoded stream data, and performs |
| bitstream level modifications without performing decoding. |
| .SH "BITSTREAM FILTERS" |
| .IX Header "BITSTREAM FILTERS" |
| When you configure your FFmpeg build, all the supported bitstream |
| filters are enabled by default. You can list all available ones using |
| the configure option \f(CW\*(C`\-\-list\-bsfs\*(C'\fR. |
| .PP |
| You can disable all the bitstream filters using the configure option |
| \&\f(CW\*(C`\-\-disable\-bsfs\*(C'\fR, and selectively enable any bitstream filter using |
| the option \f(CW\*(C`\-\-enable\-bsf=BSF\*(C'\fR, or you can disable a particular |
| bitstream filter using the option \f(CW\*(C`\-\-disable\-bsf=BSF\*(C'\fR. |
| .PP |
| The option \f(CW\*(C`\-bsfs\*(C'\fR of the ff* tools will display the list of |
| all the supported bitstream filters included in your build. |
| .PP |
| Below is a description of the currently available bitstream filters. |
| .Sh "aac_adtstoasc" |
| .IX Subsection "aac_adtstoasc" |
| Convert \s-1MPEG\-2/4\s0 \s-1AAC\s0 \s-1ADTS\s0 to \s-1MPEG\-4\s0 Audio Specific Configuration |
| bitstream filter. |
| .PP |
| This filter creates an \s-1MPEG\-4\s0 AudioSpecificConfig from an \s-1MPEG\-2/4\s0 |
| \&\s-1ADTS\s0 header and removes the \s-1ADTS\s0 header. |
| .PP |
| This is required for example when copying an \s-1AAC\s0 stream from a raw |
| \&\s-1ADTS\s0 \s-1AAC\s0 container to a \s-1FLV\s0 or a \s-1MOV/MP4\s0 file. |
| .Sh "chomp" |
| .IX Subsection "chomp" |
| Remove zero padding at the end of a packet. |
| .Sh "dump_extra" |
| .IX Subsection "dump_extra" |
| Add extradata to the beginning of the filtered packets. |
| .PP |
| The additional argument specifies which packets should be filtered. |
| It accepts the values: |
| .IP "\fBa\fR" 4 |
| .IX Item "a" |
| add extradata to all key packets, but only if \fIlocal_header\fR is |
| set in the \fBflags2\fR codec context field |
| .IP "\fBk\fR" 4 |
| .IX Item "k" |
| add extradata to all key packets |
| .IP "\fBe\fR" 4 |
| .IX Item "e" |
| add extradata to all packets |
| .PP |
| If not specified it is assumed \fBk\fR. |
| .PP |
| For example the following \fBffmpeg\fR command forces a global |
| header (thus disabling individual packet headers) in the H.264 packets |
| generated by the \f(CW\*(C`libx264\*(C'\fR encoder, but corrects them by adding |
| the header stored in extradata to the key packets: |
| .PP |
| .Vb 1 |
| \& ffmpeg -i INPUT -map 0 -flags:v +global_header -c:v libx264 -bsf:v dump_extra out.ts |
| .Ve |
| .Sh "h264_mp4toannexb" |
| .IX Subsection "h264_mp4toannexb" |
| Convert an H.264 bitstream from length prefixed mode to start code |
| prefixed mode (as defined in the Annex B of the ITU-T H.264 |
| specification). |
| .PP |
| This is required by some streaming formats, typically the \s-1MPEG\-2\s0 |
| transport stream format (\*(L"mpegts\*(R"). |
| .PP |
| For example to remux an \s-1MP4\s0 file containing an H.264 stream to mpegts |
| format with \fBffmpeg\fR, you can use the command: |
| .PP |
| .Vb 1 |
| \& ffmpeg -i INPUT.mp4 -codec copy -bsf:v h264_mp4toannexb OUTPUT.ts |
| .Ve |
| .Sh "imx_dump_header" |
| .IX Subsection "imx_dump_header" |
| .Sh "mjpeg2jpeg" |
| .IX Subsection "mjpeg2jpeg" |
| Convert \s-1MJPEG/AVI1\s0 packets to full \s-1JPEG/JFIF\s0 packets. |
| .PP |
| \&\s-1MJPEG\s0 is a video codec wherein each video frame is essentially a |
| \&\s-1JPEG\s0 image. The individual frames can be extracted without loss, |
| e.g. by |
| .PP |
| .Vb 1 |
| \& ffmpeg -i ../some_mjpeg.avi -c:v copy frames_%d.jpg |
| .Ve |
| .PP |
| Unfortunately, these chunks are incomplete \s-1JPEG\s0 images, because |
| they lack the \s-1DHT\s0 segment required for decoding. Quoting from |
| <\fBhttp://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml\fR>: |
| .PP |
| Avery Lee, writing in the rec.video.desktop newsgroup in 2001, |
| commented that \*(L"\s-1MJPEG\s0, or at least the \s-1MJPEG\s0 in AVIs having the |
| \&\s-1MJPG\s0 fourcc, is restricted \s-1JPEG\s0 with a fixed \*(-- and *omitted* \*(-- |
| Huffman table. The \s-1JPEG\s0 must be YCbCr colorspace, it must be 4:2:2, |
| and it must use basic Huffman encoding, not arithmetic or |
| progressive. . . . You can indeed extract the \s-1MJPEG\s0 frames and |
| decode them with a regular \s-1JPEG\s0 decoder, but you have to prepend |
| the \s-1DHT\s0 segment to them, or else the decoder won't have any idea |
| how to decompress the data. The exact table necessary is given in |
| the OpenDML spec.\*(R" |
| .PP |
| This bitstream filter patches the header of frames extracted from an \s-1MJPEG\s0 |
| stream (carrying the \s-1AVI1\s0 header \s-1ID\s0 and lacking a \s-1DHT\s0 segment) to |
| produce fully qualified \s-1JPEG\s0 images. |
| .PP |
| .Vb 3 |
| \& ffmpeg -i mjpeg-movie.avi -c:v copy -bsf:v mjpeg2jpeg frame_%d.jpg |
| \& exiftran -i -9 frame*.jpg |
| \& ffmpeg -i frame_%d.jpg -c:v copy rotated.avi |
| .Ve |
| .Sh "mjpega_dump_header" |
| .IX Subsection "mjpega_dump_header" |
| .Sh "movsub" |
| .IX Subsection "movsub" |
| .Sh "mp3_header_compress" |
| .IX Subsection "mp3_header_compress" |
| .Sh "mp3_header_decompress" |
| .IX Subsection "mp3_header_decompress" |
| .Sh "noise" |
| .IX Subsection "noise" |
| .Sh "remove_extra" |
| .IX Subsection "remove_extra" |
| .SH "SEE ALSO" |
| .IX Header "SEE ALSO" |
| \&\fIffmpeg\fR\|(1), \fIffplay\fR\|(1), \fIffprobe\fR\|(1), \fIffserver\fR\|(1), \fIlibavcodec\fR\|(3) |
| .SH "AUTHORS" |
| .IX Header "AUTHORS" |
| The FFmpeg developers. |
| .PP |
| For details about the authorship, see the Git history of the project |
| (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command |
| \&\fBgit log\fR in the FFmpeg source directory, or browsing the |
| online repository at <\fBhttp://source.ffmpeg.org\fR>. |
| .PP |
| Maintainers for the specific components are listed in the file |
| \&\fI\s-1MAINTAINERS\s0\fR in the source code tree. |