Preparing To Start

The first requirement to consider is encoding. We have a combination of MPEG-2 and MPEG-4 encoded video. All video will need to be MPEG-2, so we already know some of the video will have to be re-encoded. Some of the video will be sped up, while some will have pulldown used to correct the framerate. Either could be done without re-encoding. However, since none of the files have a resolution legal for PAL DVD-Video discs they'll all need re-encoding.

The files which are encoded at 23.976fps contain the original film frames. That means we can simply change the playback speed and re-encode at the correct resolution and framerate. Others are encoded at 29.97fps interlaced. With some basic information about these files we can try to recover the original film frames and discard everything else. The video can then be treated just like the 23.976fps source files. Finally, the last file appears to have hard pulldown, but is somehow deinterlaced to make it progressive. This must be treated basically like the 29.97fps interlaced video, but will require a little more trial and error to find the correct settings.

Field Dominance

By creating an index of our MPEG-2 files in DGIndex, we'll be able to access information our software will need for reassemble the original film sources from interlaced video. We also have an MPEG-4 file that's had hard pulldown used to create it, but since it was encoded progressive, there's no longer a field order to help us deconstruct the process. We'll have to use a little trial and error instead.

Framerate Change

Once we have the original frames, the framerate can be changed. We'll be using AviSynth to convert from the 23.976fps film speed used to create NTSC video to 25fps, which we've already done while demuxing audio. Now we'll need to do the same with the video. Unlike the audio, which needed to be resampled, the video will need to be re-encoded.

Resizing

Since most of our files are in NTSC Full D1 resolution (720x480) we'll be resizing everything to PAL Full D1 resolution (720x576). This will be handled by AviSynth, and you'll have several different resizers to choose from.

Optional Information

Depending on what MPEG encoder we're going to be using for the next step, encoding video assets, we may also need some colorimetry information. Colorimetry is a set of formulas used to convert RGB color into MPEG's YUV format. Most sources use only a couple of standards, including Rec.709 from the International Telecommunications Union (ITU), which is equivalent SMPTE 240M from the Society of Motion Picture and Television Engineers (SMPTE) and Rec.601 or the equivalent SMPTE 170M .

DVD compliance requires the use of Rec.709, which is what a standard MPEG encoder will use. However, the encoder also needs to know what colorimetry the source was encoded with in order to read the video to be encoded. Most encoders can detect this, but Cinemacraft Encoder Basic, one of the encoders that can be used for the next step, assumes Rec.601 for the input video. This results in colors that are "slightly off" when the input source uses some other colorimetry. DGIndex will be able to tell us each MPEG-2 file's colorimetry. Since all MPEG-4 ASP encoders encode in Rec.601 we'll assume that for the rest of our files.