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129 | .\" ======================================================================== |
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130 | .\" |
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131 | .IX Title "FFMPEG-BITSTREAM-FILTERS 1" |
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132 | .TH FFMPEG-BITSTREAM-FILTERS 1 "2013-12-14" " " " " |
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133 | .SH "NAME" |
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134 | ffmpeg\-bitstream\-filters \- FFmpeg bitstream filters |
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135 | .SH "DESCRIPTION" |
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136 | .IX Header "DESCRIPTION" |
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137 | This document describes the bitstream filters provided by the |
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138 | libavcodec library. |
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139 | .PP |
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140 | A bitstream filter operates on the encoded stream data, and performs |
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141 | bitstream level modifications without performing decoding. |
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142 | .SH "BITSTREAM FILTERS" |
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143 | .IX Header "BITSTREAM FILTERS" |
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144 | When you configure your FFmpeg build, all the supported bitstream |
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145 | filters are enabled by default. You can list all available ones using |
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146 | the configure option \f(CW\*(C`\-\-list\-bsfs\*(C'\fR. |
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147 | .PP |
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148 | You can disable all the bitstream filters using the configure option |
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149 | \&\f(CW\*(C`\-\-disable\-bsfs\*(C'\fR, and selectively enable any bitstream filter using |
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150 | the option \f(CW\*(C`\-\-enable\-bsf=BSF\*(C'\fR, or you can disable a particular |
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151 | bitstream filter using the option \f(CW\*(C`\-\-disable\-bsf=BSF\*(C'\fR. |
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152 | .PP |
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153 | The option \f(CW\*(C`\-bsfs\*(C'\fR of the ff* tools will display the list of |
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154 | all the supported bitstream filters included in your build. |
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155 | .PP |
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156 | Below is a description of the currently available bitstream filters. |
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157 | .Sh "aac_adtstoasc" |
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158 | .IX Subsection "aac_adtstoasc" |
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159 | Convert \s-1MPEG\-2/4\s0 \s-1AAC\s0 \s-1ADTS\s0 to \s-1MPEG\-4\s0 Audio Specific Configuration |
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160 | bitstream filter. |
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161 | .PP |
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162 | This filter creates an \s-1MPEG\-4\s0 AudioSpecificConfig from an \s-1MPEG\-2/4\s0 |
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163 | \&\s-1ADTS\s0 header and removes the \s-1ADTS\s0 header. |
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164 | .PP |
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165 | This is required for example when copying an \s-1AAC\s0 stream from a raw |
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166 | \&\s-1ADTS\s0 \s-1AAC\s0 container to a \s-1FLV\s0 or a \s-1MOV/MP4\s0 file. |
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167 | .Sh "chomp" |
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168 | .IX Subsection "chomp" |
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169 | Remove zero padding at the end of a packet. |
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170 | .Sh "dump_extra" |
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171 | .IX Subsection "dump_extra" |
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172 | Add extradata to the beginning of the filtered packets. |
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173 | .PP |
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174 | The additional argument specifies which packets should be filtered. |
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175 | It accepts the values: |
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176 | .IP "\fBa\fR" 4 |
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177 | .IX Item "a" |
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178 | add extradata to all key packets, but only if \fIlocal_header\fR is |
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179 | set in the \fBflags2\fR codec context field |
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180 | .IP "\fBk\fR" 4 |
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181 | .IX Item "k" |
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182 | add extradata to all key packets |
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183 | .IP "\fBe\fR" 4 |
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184 | .IX Item "e" |
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185 | add extradata to all packets |
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186 | .PP |
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187 | If not specified it is assumed \fBk\fR. |
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188 | .PP |
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189 | For example the following \fBffmpeg\fR command forces a global |
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190 | header (thus disabling individual packet headers) in the H.264 packets |
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191 | generated by the \f(CW\*(C`libx264\*(C'\fR encoder, but corrects them by adding |
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192 | the header stored in extradata to the key packets: |
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193 | .PP |
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194 | .Vb 1 |
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195 | \& ffmpeg -i INPUT -map 0 -flags:v +global_header -c:v libx264 -bsf:v dump_extra out.ts |
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196 | .Ve |
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197 | .Sh "h264_mp4toannexb" |
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198 | .IX Subsection "h264_mp4toannexb" |
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199 | Convert an H.264 bitstream from length prefixed mode to start code |
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200 | prefixed mode (as defined in the Annex B of the ITU-T H.264 |
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201 | specification). |
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202 | .PP |
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203 | This is required by some streaming formats, typically the \s-1MPEG\-2\s0 |
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204 | transport stream format (\*(L"mpegts\*(R"). |
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205 | .PP |
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206 | For example to remux an \s-1MP4\s0 file containing an H.264 stream to mpegts |
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207 | format with \fBffmpeg\fR, you can use the command: |
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208 | .PP |
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209 | .Vb 1 |
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210 | \& ffmpeg -i INPUT.mp4 -codec copy -bsf:v h264_mp4toannexb OUTPUT.ts |
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211 | .Ve |
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212 | .Sh "imx_dump_header" |
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213 | .IX Subsection "imx_dump_header" |
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214 | .Sh "mjpeg2jpeg" |
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215 | .IX Subsection "mjpeg2jpeg" |
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216 | Convert \s-1MJPEG/AVI1\s0 packets to full \s-1JPEG/JFIF\s0 packets. |
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217 | .PP |
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218 | \&\s-1MJPEG\s0 is a video codec wherein each video frame is essentially a |
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219 | \&\s-1JPEG\s0 image. The individual frames can be extracted without loss, |
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220 | e.g. by |
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221 | .PP |
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222 | .Vb 1 |
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223 | \& ffmpeg -i ../some_mjpeg.avi -c:v copy frames_%d.jpg |
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224 | .Ve |
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225 | .PP |
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226 | Unfortunately, these chunks are incomplete \s-1JPEG\s0 images, because |
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227 | they lack the \s-1DHT\s0 segment required for decoding. Quoting from |
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228 | <\fBhttp://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml\fR>: |
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229 | .PP |
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230 | Avery Lee, writing in the rec.video.desktop newsgroup in 2001, |
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231 | commented that \*(L"\s-1MJPEG\s0, or at least the \s-1MJPEG\s0 in AVIs having the |
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232 | \&\s-1MJPG\s0 fourcc, is restricted \s-1JPEG\s0 with a fixed \*(-- and *omitted* \*(-- |
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233 | Huffman table. The \s-1JPEG\s0 must be YCbCr colorspace, it must be 4:2:2, |
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234 | and it must use basic Huffman encoding, not arithmetic or |
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235 | progressive. . . . You can indeed extract the \s-1MJPEG\s0 frames and |
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236 | decode them with a regular \s-1JPEG\s0 decoder, but you have to prepend |
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237 | the \s-1DHT\s0 segment to them, or else the decoder won't have any idea |
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238 | how to decompress the data. The exact table necessary is given in |
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239 | the OpenDML spec.\*(R" |
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240 | .PP |
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241 | This bitstream filter patches the header of frames extracted from an \s-1MJPEG\s0 |
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242 | stream (carrying the \s-1AVI1\s0 header \s-1ID\s0 and lacking a \s-1DHT\s0 segment) to |
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243 | produce fully qualified \s-1JPEG\s0 images. |
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244 | .PP |
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245 | .Vb 3 |
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246 | \& ffmpeg -i mjpeg-movie.avi -c:v copy -bsf:v mjpeg2jpeg frame_%d.jpg |
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247 | \& exiftran -i -9 frame*.jpg |
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248 | \& ffmpeg -i frame_%d.jpg -c:v copy rotated.avi |
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249 | .Ve |
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250 | .Sh "mjpega_dump_header" |
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251 | .IX Subsection "mjpega_dump_header" |
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252 | .Sh "movsub" |
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253 | .IX Subsection "movsub" |
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254 | .Sh "mp3_header_compress" |
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255 | .IX Subsection "mp3_header_compress" |
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256 | .Sh "mp3_header_decompress" |
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257 | .IX Subsection "mp3_header_decompress" |
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258 | .Sh "noise" |
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259 | .IX Subsection "noise" |
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260 | .Sh "remove_extra" |
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261 | .IX Subsection "remove_extra" |
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262 | .SH "SEE ALSO" |
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263 | .IX Header "SEE ALSO" |
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264 | \&\fIffmpeg\fR\|(1), \fIffplay\fR\|(1), \fIffprobe\fR\|(1), \fIffserver\fR\|(1), \fIlibavcodec\fR\|(3) |
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265 | .SH "AUTHORS" |
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266 | .IX Header "AUTHORS" |
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267 | The FFmpeg developers. |
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268 | .PP |
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269 | For details about the authorship, see the Git history of the project |
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270 | (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command |
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271 | \&\fBgit log\fR in the FFmpeg source directory, or browsing the |
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272 | online repository at <\fBhttp://source.ffmpeg.org\fR>. |
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273 | .PP |
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274 | Maintainers for the specific components are listed in the file |
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275 | \&\fI\s-1MAINTAINERS\s0\fR in the source code tree.\fBhttp://source.ffmpeg.org\fR>\fBhttp://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml\fR>>> |