doc/biamove-doc.html

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   5 >BiaMovE documentation</TITLE
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  10 CLASS="BOOK"
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  16 ><DIV
  17 CLASS="TITLEPAGE"
  18 ><H1
  19 CLASS="TITLE"
  20 ><A
  21 NAME="AEN1"
  22 ><SPAN
  23 CLASS="APPLICATION"
  24 >BiaMovE</SPAN
  25 > documentation</A
  26 ></H1
  27 ><H3
  28 CLASS="AUTHOR"
  29 ><A
  30 NAME="AEN5"
  31 ></A
  32 >Harishankar V</H3
  33 ><DIV
  34 ><DIV
  35 CLASS="ABSTRACT"
  36 ><P
  37 ></P
  38 ><A
  39 NAME="AEN8"
  40 ></A
  41 ><P
  42 >A short guide to video encoding using <SPAN
  43 CLASS="APPLICATION"
  44 >BiaMovE</SPAN
  45 > (via <SPAN
  46 CLASS="APPLICATION"
  47 >Mencoder</SPAN
  48 >)</P
  49 ><P
  50 ></P
  51 ></DIV
  52 ></DIV
  53 ><HR></DIV
  54 ><DIV
  55 CLASS="TOC"
  56 ><DL
  57 ><DT
  58 ><B
  59 >Table of Contents</B
  60 ></DT
  61 ><DT
  62 >1. <A
  63 HREF="#INTRO"
  64 >Introduction</A
  65 ></DT
  66 ><DD
  67 ><DL
  68 ><DT
  69 ><A
  70 HREF="#WHY"
  71 >Why <SPAN
  72 CLASS="APPLICATION"
  73 >Mencoder</SPAN
  74 ></A
  75 ></DT
  76 ><DT
  77 ><A
  78 HREF="#PHILOSOPHY"
  79 >Philosophy</A
  80 ></DT
  81 ></DL
  82 ></DD
  83 ><DT
  84 >2. <A
  85 HREF="#VIDEOBASICS"
  86 >Video encoding basics</A
  87 ></DT
  88 ><DD
  89 ><DL
  90 ><DT
  91 ><A
  92 HREF="#THEPROBLEMS"
  93 >The problems</A
  94 ></DT
  95 ><DT
  96 ><A
  97 HREF="#CONCEPTS"
  98 >Concepts</A
  99 ></DT
 100 ><DD
 101 ><DL
 102 ><DT
 103 ><A
 104 HREF="#BITRATE"
 105 >Bitrate</A
 106 ></DT
 107 ><DT
 108 ><A
 109 HREF="#FRAMERATE"
 110 >Framerate</A
 111 ></DT
 112 ></DL
 113 ></DD
 114 ></DL
 115 ></DD
 116 ></DL
 117 ></DIV
 118 ><DIV
 119 CLASS="CHAPTER"
 120 ><HR><H1
 121 ><A
 122 NAME="INTRO"
 123 ></A
 124 >Chapter 1. Introduction</H1
 125 ><P
 126 >                       <SPAN
 127 CLASS="APPLICATION"
 128 >BiaMovE</SPAN
 129 > (pronounced "by-a-movie") is a graphical user interface to <A
 130 HREF="http://www.mplayerhq.hu/"
 131 TARGET="_top"
 132 ><SPAN
 133 CLASS="APPLICATION"
 134 >Mencoder</SPAN
 135 ></A
 136 >, an extremely powerful and versatile cross-platform video encoding command-line utility. The problem with <SPAN
 137 CLASS="APPLICATION"
 138 >Mencoder</SPAN
 139 > is that it is very complex and non-trivial to lay users.
 140                 </P
 141 ><P
 142 >                       Adding to the complexity is the existence/non-existence of video/audio codecs, proprietary technologies and technical terminology related to audio and video. I had a very difficult time poring over the <SPAN
 143 CLASS="APPLICATION"
 144 >Mencoder</SPAN
 145 > documentation to find specific options so I decided that while I was learning how to use it, why not create a GUI front-end for it?
 146                 </P
 147 ><DIV
 148 CLASS="SECT1"
 149 ><HR><H2
 150 CLASS="SECT1"
 151 ><A
 152 NAME="WHY"
 153 >Why <SPAN
 154 CLASS="APPLICATION"
 155 >Mencoder</SPAN
 156 ></A
 157 ></H2
 158 ><P
 159 >                               Why <SPAN
 160 CLASS="APPLICATION"
 161 >Mencoder</SPAN
 162 > and why not <SPAN
 163 CLASS="APPLICATION"
 164 >FFMpeg</SPAN
 165 >? Well, for one, <SPAN
 166 CLASS="APPLICATION"
 167 >Mencoder</SPAN
 168 > can wrap around <SPAN
 169 CLASS="APPLICATION"
 170 >FFMpeg</SPAN
 171 > libraries using <TT
 172 CLASS="FILENAME"
 173 >libavcodec</TT
 174 >. Secondly I found using the <SPAN
 175 CLASS="APPLICATION"
 176 >FFMpeg</SPAN
 177 > command line much easier than <SPAN
 178 CLASS="APPLICATION"
 179 >Mencoder</SPAN
 180 > and felt that it would be better to write a GUI around <SPAN
 181 CLASS="APPLICATION"
 182 >Mencoder</SPAN
 183 > instead.
 184                         </P
 185 ></DIV
 186 ><DIV
 187 CLASS="SECT1"
 188 ><HR><H2
 189 CLASS="SECT1"
 190 ><A
 191 NAME="PHILOSOPHY"
 192 >Philosophy</A
 193 ></H2
 194 ><P
 195 >                               When I wrote <SPAN
 196 CLASS="APPLICATION"
 197 >BiaMovE</SPAN
 198 > I wanted to mainly explore the codec-specific options of <SPAN
 199 CLASS="APPLICATION"
 200 >Mencoder</SPAN
 201 >. I did so because video/audio codecs are extremely complex creatures. I cannot pretend that I understood everything I read in the <SPAN
 202 CLASS="APPLICATION"
 203 >Mencoder</SPAN
 204 > manual pages. With <SPAN
 205 CLASS="APPLICATION"
 206 >BiaMovE</SPAN
 207 > I've tried to hide a little bit of the complexity, but without restricting the advanced user.
 208                         </P
 209 ><P
 210 >                               <SPAN
 211 CLASS="APPLICATION"
 212 >BiaMovE</SPAN
 213 > is not a tool for the newbie though. It is just a thin (albeit useful) GUI wrapper to <SPAN
 214 CLASS="APPLICATION"
 215 >Mencoder</SPAN
 216 >. It does <SPAN
 217 CLASS="emphasis"
 218 ><I
 219 CLASS="EMPHASIS"
 220 >not</I
 221 ></SPAN
 222 >:
 223                                 <P
 224 ></P
 225 ><UL
 226 ><LI
 227 ><P
 228 >Check for the sanity of your <SPAN
 229 CLASS="APPLICATION"
 230 >Mencoder</SPAN
 231 > configuration, nor does it check for codec availability on your setup.</P
 232 ></LI
 233 ><LI
 234 ><P
 235 >Does not verify the sanity of your options. It just passes on your choices to the underlying <SPAN
 236 CLASS="APPLICATION"
 237 >Mencoder</SPAN
 238 > command line.</P
 239 ></LI
 240 ></UL
 241 >
 242                         </P
 243 ><P
 244 >                               Along the way, I've been bumbling along, discovering by trial and error, by experimentation and research, the proper way to mix video and audio codecs and produce valid video streams. If you are a newbie to video encoding and want to learn more, I suggest your read the section on <A
 245 HREF="#VIDEOBASICS"
 246 >video encoding basics</A
 247 > and also study the <SPAN
 248 CLASS="APPLICATION"
 249 >Mencoder</SPAN
 250 > manual pages in depth.
 251                         </P
 252 ></DIV
 253 ></DIV
 254 ><DIV
 255 CLASS="CHAPTER"
 256 ><HR><H1
 257 ><A
 258 NAME="VIDEOBASICS"
 259 ></A
 260 >Chapter 2. Video encoding basics</H1
 261 ><P
 262 >                       Before you jump into video encoding, it's useful to understand a few video (and audio) related concepts. This will help you exploit the full power of <SPAN
 263 CLASS="APPLICATION"
 264 >BiaMovE</SPAN
 265 > and <SPAN
 266 CLASS="APPLICATION"
 267 >Mencoder</SPAN
 268 >. While most of the information here is common knowledge, I've documented some of my thoughts and discoveries in an easily accessible manner. However, before you dive in, I suggest you read the <A
 269 HREF="#CONCEPTS"
 270 >concepts</A
 271 > section for definitions to common terms specific to digital audio/video technologies.
 272                 </P
 273 ><P
 274 >                       If you are of the "just want to rip my DVDs to my iPod" type, feel free to skip this section.
 275                 </P
 276 ><DIV
 277 CLASS="SECT1"
 278 ><HR><H2
 279 CLASS="SECT1"
 280 ><A
 281 NAME="THEPROBLEMS"
 282 >The problems</A
 283 ></H2
 284 ><P
 285 >                               For most people simply using a command-line tool like <SPAN
 286 CLASS="APPLICATION"
 287 >Mencoder</SPAN
 288 > can be a daunting task. The <SPAN
 289 CLASS="APPLICATION"
 290 >Mencoder</SPAN
 291 > manual page alone is scary enough, because it documents both the player <SPAN
 292 CLASS="APPLICATION"
 293 >MPlayer</SPAN
 294 > as well as the encoder.
 295                         </P
 296 ><P
 297 >                               Apart from the command-line itself, video and audio codecs are complex and tricky subjects in themselves. Apart from the variety of standards and formats adopted by different organizations (for instance, <ABBR
 298 CLASS="ABBREV"
 299 >MPEG-4</ABBR
 300 >, <ABBR
 301 CLASS="ABBREV"
 302 >H.264</ABBR
 303 >, <ACRONYM
 304 CLASS="ACRONYM"
 305 >DivX</ACRONYM
 306 >, <ACRONYM
 307 CLASS="ACRONYM"
 308 >XViD</ACRONYM
 309 > etc.), there exists hundreds of specifications within even these formats. Worse still, many of these standards are not compatible with each other and many video players, particularly hardware players, do not recognize open standards codecs (the <SPAN
 310 CLASS="TRADEMARK"
 311 >Apple iPod</SPAN
 312 >&#8482; is a case in point).
 313                         </P
 314 ><P
 315 >                               Complicating it is the fact that not all muxers (container formats) work with all codecs and not all video and audio codecs are compatible with each other. Again, certain codecs provide very sane default parameters while other codecs require to be told exactly how to encode the underlying data. Last, but not least, some codecs are plain buggy and broken or don't work very well with <SPAN
 316 CLASS="APPLICATION"
 317 >Mencoder</SPAN
 318 >.
 319                         </P
 320 ><P
 321 >                               <SPAN
 322 CLASS="APPLICATION"
 323 >BiaMovE</SPAN
 324 > cannot overcome these problems for you for the reasons already mentioned earlier. However reading these notes should help you avoid some of the pitfalls.
 325                         </P
 326 ></DIV
 327 ><DIV
 328 CLASS="SECT1"
 329 ><HR><H2
 330 CLASS="SECT1"
 331 ><A
 332 NAME="CONCEPTS"
 333 >Concepts</A
 334 ></H2
 335 ><DIV
 336 CLASS="SECT2"
 337 ><H3
 338 CLASS="SECT2"
 339 ><A
 340 NAME="BITRATE"
 341 >Bitrate</A
 342 ></H3
 343 ><P
 344 >                                       Bitrate is the number of bits which encode the information per unit of time. It is usually measured in kilobits per second (kbit/s) or megabits per second (mbit/s). In practical terms, higher the bitrate, higher the quality of the information stored (whether video or audio).
 345                                 </P
 346 ><P
 347 >                                       The best bitrate depends on several factors including desired video/audio quality versus size trade-off, the resolution of the video as well as the number of frames per second.
 348                                 </P
 349 ></DIV
 350 ><DIV
 351 CLASS="SECT2"
 352 ><HR><H3
 353 CLASS="SECT2"
 354 ><A
 355 NAME="FRAMERATE"
 356 >Framerate</A
 357 ></H3
 358 ><P
 359 >                                       Framerate is the number of frames per unit time. Frames may be audio or video frames. Think of a single frame as a still. Over the years, different video standards (<ACRONYM
 360 CLASS="ACRONYM"
 361 >PAL</ACRONYM
 362 >, <ABBR
 363 CLASS="ABBREV"
 364 >NTSC</ABBR
 365 > etc.) have evolved and use standard framerates (24.997 fps, 25 fps, 29.997 fps, 30 fps etc.) but theoritically any video can have any framerate or even variable framerates.
 366                                 </P
 367 ><P
 368 >                                       The higher the framerate, smoother the animation. Usually 25 to 30 fps is more than enough for the human eye.
 369                                 </P
 370 ></DIV
 371 ></DIV
 372 ></DIV
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