Introduction
Every DVD+RW video recorder is based on the DVD+RW Real Time Video Format. This format was designed to be 100% compatible with existing DVD-Video players. It therefore does not describe the way the video and audio is supposed to be encoded, as this is already covered in the DVD-Video specification. It does however describe the way the disc is supposed to behave on a DVD+RW recorder while recording, or how it should be played on a DVD-Video player. This article will give you a closer look at some of the features of the DVD+RW Real Time Video Format.


Video modes and resolutions
DVD+RW video recorders offer the user a number of video modes to select from prior to recording. The video modes allow the user to decide wether to go for the best possible picture quality, or select a lesser degree of quality while gaining more recording time. Irrespective of the selected recording mode, all recordings are DVD-Video compatible and all can be played on a DVD-Video player.

The recording modes are:

HQ - High Quaility (1 hour per side)
720 x 576 pixels - 9.72 Mbit/sec VBR
SP - Standard Play (2 hours per side)
720 x 576 pixels - 5.07 Mbit/sec VBR
LP - Long Play (3 hours per side)
360 x 576 pixels - 3.38 Mbit/sec VBR
EP - Extended Play (4 hours per side)
360 x 576 pixels - 2.54 Mbit/sec VBR

These values are for PAL recordings, NTSC has a vertical resolution of 480 lines instead of 576.

The video modes can freely be interchanged on a single disc, i.e. one can make a recording of 1 hour in SP quaility on a disc, and then add a 2 hour recording in EP format to it. At playback, the correct playback mode will be detected, even when played back on a normal DVD-Video player.

Audio will be coded using the Dolby Digital format in two-channel stereo, with a sampling rate of 48 KHz, using 16 bit per sample. Audio-quality will therefore be comparable to a DAT-recording.


Titles and chapters
Every new recording will automatically be asigned a new chapter number, and a new entry for the recording will be added to the index picture screen (see next paragraph). All titles on a disc will be chained, that is, when playback of a title is started, all consequent titles will also be played (this way, the behaviour of a disc recorded on a DVD+RW recorder is comparable to a VCR).

Each title can be devided into chapters for easy reference. This can be done automatically by the recorder at standard intervals (about 5 minutes), or the chapter markers can be placed by the user himself. When playing back the disc on the recorder or a DVD-Video player, one can use the Next and Previous buttons on the remote control to go to the consequent chapter point. While pressing next during playback of the last chapter will advance to the beginning of the next title, since all titles are chained together.

It is also possible to devide a title into multiple titles, an operation that cannot be undone afterwards. The advantage of doing so is that the "new" title will be asigned its own entry (with accompanying picture) in the Index Picture Screen.


Index Picture Screen (menus)
After the first recording is made to a blank DVD+RW disc, a menu will automatically be created that will contain an image representing the recording, along with the name of the recording, the duration of the recording, the selected recording mode and the date of recording. If the station broadcasted the program name (using for example a Teletext transmission), this name of the recording will be used, otherwise the channel name plus recording date and time will be showed. The title name can be changed into a more desciptive name by the user.

After each recording, the menu will automatically be updated and new images will be added. A menu screen may contain up to 3 titles, after which an additional menu screen will be created. The user will be able to select one of the images on screen to select the recording that should be played, pressing down while the third image is highlighted will show the next menu screen.

The name of the individial recordings can always be changed afterwards by the user. Also the index picture, which is automatically selected upon by the recorder, can be changed by the user by selecting any of the video frames of the respective title.

If a title was erased (see "Overwriting and erasing of recordings"), it will show up as "Free space" in the title menu. Selecting such an entry for playback on the recorder or a DVD-Video player, will result in the playback of the next title. Also, if a title has been made completely "hidden" (see "Editing"), selecting this title will start the playback of the next title.

The menu will always show up on the first index screen when the disc is placed in the recorder or a DVD-Video player (see picture). Pressing Up while the first image on the first screen is highlighted will result in the showing of the Disc Menu. The Disc Menu may also contain a name (to be entered by the user), and furthermore it contains some info on the video format (PAL/NTSC) that was used on the disc, the combined recorded time, the date of the last recording and a status on wether the edits are DVD-Video compatible yet (see next paragraph).


Editing
Titles can be edited afterwards by dividing them into chapters and selecting which titles should be played, and which should be skipped. This way, it is for example possible to skip the commercials in a recording of a movie.

When the edited title is being selected for playback on the index picture screen using the DVD+RW recorder, the edited version will always be played. The chapters that are marked "hidden" will be skipped, but chapter numbering will remain consistent with the original recording. That is, if for example chapter 2 was set hidden, the number will be skipped but the next chapter will remain to be displayed as chapter 3.

For a DVD+RW disc to play the edited titles on a DVD-Video player, the edits should first be made compatible using a menu option on the recorder. Remember that the recordings are always, immediately, DVD-Video compatible, and that only the edits need to undergo this simple operation, which will only take a few minutes. After this procedure, the titles will be played in the exact same way on a DVD-Video player as intented to by the creator. There's one minor difference: the numbering of chapters will be continuous, hidden chapters will not be shown and are completely invisible to the viewer, hence the third chapter from the example above will be displayed as chapter 2.

Hidden chapters are not removed from the disc, they can always be "restored" at a later time, or the chapter point can be replaced to make different parts of the title invisible. The edited versions of the titles (so called "Play List Titles") will be asigned the first title numbers on the disc. If needed, the full titles can always be played, both on the recorder and on a DVD-Video player, by manually selecting any of the title numbers after the play list titles. For example: on a disc with 5 titles, the title-numbers 1 trough 5 will be asigned to the playlists (wether they are edited or not), and the title-numbers 6 trough 10 refer to the full titles. Full titles are not included in the menu.


Overwriting and erasing of recordings
At any point it is possible to start recording on the disc, recording is not limited to adding new material to the end of a disc. The recording will append at the point in a title that the user has selected for starting of the recording. Video and audio will be added to the current title, it is not necessary to create a new title. Of course, it is always possible to divide the title into multiple seperate titles, as mentioned before.

If a recording is being overwritten at a certain point, and the new recording does not "last" as long as the original title that is being overwritten, the last part of the original recording will still be accessible. This behaviour is identical to overwriting a recording using a standard VCR. The remaining part of the title will be assigned it's own title number which will be included on the Index Picture Screen. If the new recording is longer than the original title, the following title(s) will be overwritten as well. If a part of the last title that is being overwritten remains on the disc, it's entry on the Index Picture Screen will remain. Selecting it will start playback of the part of the title that is still available on the disc.

A user may decide to erase a certain title. This operation, which cannot be undone, will free up the space taken up by the title. Free space will be shown in the Index Picture Screen as an empty image. If consequent titles will be erased, their free space will be combined into a single free space entry in the Index Picture Screen. Remember that it's not necessary to erase a title, as they can simple be overwritten or made "hidden". However, the option is included to erase a title from the Index Picture Screen and to prevent people from accessing it using direct title access as described under "Editing".


File format
A disc recorded in a DVD+RW video recorder will be 100% compatible with the DVD-Video specification on a logical basis. That is, the locations of video and menu files will be according to this standard, and also the format and naming of the files will be exactly the same as on a pre-recorded DVD-Video disc. Recorded programs will be stored in the VIDEO_TS directory using the normal .VOB-file format. All standard DVD-Video playback software and editing or ripping utilities on a PC can be used with DVD+RW recordings.

As allowed by the DVD-Video specification, additional files will be stored on the disc containing extra information that will be used by the DVD+RW Real Time Video Format. For example, the index pictures are also stored as individual pictures so that the recorder can read them when it needs to re-create a new index picture screen (when a recording is added or changed).


PAL and NTSC recordings
All DVD+RW recorders support for the recording in both NTSC and PAL DVD-Video format. Although the recorders have an internal tuner for a single system (i.e. PAL in Europe and NTSC in the US), they will accept other format video from an external source (such as a camcorder or VCR) and record this video as such. For playback, the DVD-Video player or the connected TV set must support this foreign format.

Since it is not possible to combine PAL and NTSC on a single disc according to the DVD-Video specification, the first recording will determine the "format" of the disc. This format will also be shown on the Disc Menu that can be accessed by pressing "Up" on the first menu page, on both the recorder and a DVD-Video player. Of course, when the disc will be completely erased, the other format can be used for recording.


Region coding
Recordings made on a DVD+RW video recorder have the region coding flag set to "off", hence the discs are not region protected in any way. A recording made on a European DVD+RW video recorder can for example be played on any DVD-Video player, even a US model.

Keep in mind however that most US DVD-Video players do not play PAL DVD-discs, so that a PAL recording can not be played. Most European DVD-Video players accept discs in both PAL and NTSC format, but depending on their output format, they also need a multi-standard TV set for playback.


Subpicture
Every recording made on a DVD+RW video recorder will contain a subpicture stream along with the recording. Subpictures are used by DVD-Video discs to show subtitles among others. Initially, these subpicture streams will be empty, however, on future releases of the DVD+RW recorder, they can be used to store additional information, such as the date of a camcorder recording or a program title.


Aspect ratio
Normally, all recordings made with a DVD+RW video recorder have a screen aspect ratio of 4:3. When you record video from an anamorphic widescreen source (such as a DV camcorder recording made in "16:9 Wide" mode), it will be recorded as such in anamorphic format on the disc. The recorder will include an extra flag in the video stream that will allow the recorder to signal the TV to swith to "widescreen" mode when playing back the disc.

Keep in mind however that this is a DVD+RW "extra feature", that is not defined by the DVD-Video specification. Hence, a DVD-Video player will not signal the TV to switch to widescreen mode, you have to do this manually. The video will also not be scaled to letterbox format when being played on a DVD player that is set to 4:3 Letterbox mode. This is all due to the fact that the DVD-Video specification does not allow for the changing of "normal" and "widescreen" mode within a single title. Since it cannot be guaranteed that a title recorded in widescreen will not contain 4:3 video at a later time, the official "anamorphic" flag will not be included, otherwise the possible 4:3 video in that same title will be showed "streched". Of course during playback on a DVD+RW video recorder, there can be a mixture of singals to indicate widescreen and 4:3 video.

When recording a widescreen TV-program, such as a PALplus transmission (that is, a letterboxed 16:9 TV-broadcast common in Europe that signals a 16:9 "zoom" command to widescreen TVs), the video will be recorded in full screen 4:3 mode, including the black bars, so that it will play correctly on any TV set. Also in this case, the "zoom"-command will be stored as a DVD+RW exclusive extra, so that playing back such a recording using a DVD+RW recorder will trigger the TV to zoom in on the actual picture.

Added:  Friday, October 18, 2002
Reviewer:  Ed

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