Scenarist and 16:9 mpeg-1 encodes

Flood · 18th September 2002, 03:33

Hi all,

Trying to build a dvd from vcd sources, specifically 16:9 mpeg-1 352x240 NTSC (progressive), 23.98 fps. Scenarist complains about the 16:9 aspect ratio being incorrect, as well as the 23.98 fps (yes, the asset is in it's own VTS).

I know that 23.98 fps is a legal frame rate for dvd, and that 16:9 is certainly allowed. I hate to have to transcode to mpeg-2 (so i can set 3:2 pulldown), does anyone know what resolutions/formats Scenarist allows?

Thanks!

oddyseus · 18th September 2002, 11:14

Most probably your bitrate is off, as Scenarist doesn't allow more than 1858kbs on mpeg1 streams.

auenf · 18th September 2002, 12:15

uhh, i think the dvd spec only supports 25 and 29.97 fps, and also supports 23.976 'FILM' when it is 'pulled down' to 29.97 with TFF and RFF flags?

Enf...

Flood · 18th September 2002, 18:23

Bitrate is standard VCD 1150kbps, so that isn't it.

Unfortunately, 16:9 issue aside, it does appear that 23.98 fps isn't supported unless 3:2 pulldown is set, which you obviously can't do on an mpeg-1 stream.

So, I guess I'll have to transcode to mpeg-2 at a high VBR bitrate and set 3:2 pulldown.

You know, it seems to me that there ought to be a way to convert mpeg-1 to mpeg-2, without re-encoding. After all, IIRC, the actual algorithm is the same, in terms if I, B & P frames, however mpeg-2 supports all the nifty header extensions, like 3:2 pulldown, fields, etc.

DIggedy · 23rd September 2002, 23:21

Flood: why would you need to use a high VBR bitrate to transcode to mpeg-2? Being that the source is low bitrate I wouldn't think you would need any higher than say 3000kbps peak to maintain the same quality.

Flood · 24th September 2002, 00:16

Because the source contains a good deal of mpeg artifacting, and re-encoding produces a good deal of quantization (i.e. mpeg doesn't deal very well with noisy source).

I ended up with an average bitrate of about 3500 kbps, peaking up to 7-8 mbps during action-heavy scenes. While the re-encode is slightly lossy, it's only barely noticable. I probably could have jacked the bitrate way up, and had no noticable loss, however disc space was a concern (trying to fit four 45 minute episodes on one dvd + menus), so I opted for some loss.

18th September 2002, 03:33	#1 \| Link
Flood Registered User Join Date: Aug 2002 Posts: 12	Scenarist and 16:9 mpeg-1 encodes Hi all, Trying to build a dvd from vcd sources, specifically 16:9 mpeg-1 352x240 NTSC (progressive), 23.98 fps. Scenarist complains about the 16:9 aspect ratio being incorrect, as well as the 23.98 fps (yes, the asset is in it's own VTS). I know that 23.98 fps is a legal frame rate for dvd, and that 16:9 is certainly allowed. I hate to have to transcode to mpeg-2 (so i can set 3:2 pulldown), does anyone know what resolutions/formats Scenarist allows? Thanks!

18th September 2002, 11:14	#2 \| Link
oddyseus Registered User Join Date: Feb 2002 Location: Hellas Posts: 1,598	Most probably your bitrate is off, as Scenarist doesn't allow more than 1858kbs on mpeg1 streams. __________________ regards oddyseus "when u r aiming for the impossible everything else is within reach." Mike ps. respect the forum rules, read, search and only then post.

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18th September 2002, 12:15	#3 \| Link
auenf avatar doesn't support IE Join Date: Feb 2002 Location: The Great Southland Posts: 2,238	uhh, i think the dvd spec only supports 25 and 29.97 fps, and also supports 23.976 'FILM' when it is 'pulled down' to 29.97 with TFF and RFF flags? Enf...

18th September 2002, 18:23	#4 \| Link
Flood Registered User Join Date: Aug 2002 Posts: 12	Bitrate is standard VCD 1150kbps, so that isn't it. Unfortunately, 16:9 issue aside, it does appear that 23.98 fps isn't supported unless 3:2 pulldown is set, which you obviously can't do on an mpeg-1 stream. So, I guess I'll have to transcode to mpeg-2 at a high VBR bitrate and set 3:2 pulldown. You know, it seems to me that there ought to be a way to convert mpeg-1 to mpeg-2, without re-encoding. After all, IIRC, the actual algorithm is the same, in terms if I, B & P frames, however mpeg-2 supports all the nifty header extensions, like 3:2 pulldown, fields, etc.

23rd September 2002, 23:21	#5 \| Link
DIggedy Registered User Join Date: Aug 2002 Location: Sydney, Australia Posts: 157	Flood: why would you need to use a high VBR bitrate to transcode to mpeg-2? Being that the source is low bitrate I wouldn't think you would need any higher than say 3000kbps peak to maintain the same quality.

24th September 2002, 00:16	#6 \| Link
Flood Registered User Join Date: Aug 2002 Posts: 12	Because the source contains a good deal of mpeg artifacting, and re-encoding produces a good deal of quantization (i.e. mpeg doesn't deal very well with noisy source). I ended up with an average bitrate of about 3500 kbps, peaking up to 7-8 mbps during action-heavy scenes. While the re-encode is slightly lossy, it's only barely noticable. I probably could have jacked the bitrate way up, and had no noticable loss, however disc space was a concern (trying to fit four 45 minute episodes on one dvd + menus), so I opted for some loss.