Question for MPEG Streamclip users...

[terryj]

Ok, so I downloaded and thought I'd try it out
on a problematic MPG file I've had on my desk for a
while. Normally I would just use ffmpegx to demux,
but when I demux the file with ffmpegx, it gets noticeably choppier
than in its muxed version, which is clean and clear.

So I gave MPEG Streamclip a try, and using the "Demux to
m2v and Aiff" command, I get my elementry streams,
and the video plays fine to about halfway through, and then
blockiness occurs.

Yet the muxed MPEG plays fine in QT and VLC. Burns fine
as is to VCD through Toast with no re-encoding.

Just curious as to what could be causing it, or is their
some magic settings in MPEG Streamclip I should look at.
I didn't set anything, figured it would work "straight out of the box".

thanks.

[terryj]

Seems like I solved my own Problem.
For whatever reason, I don't know, but
I went back into Prefs, and chose the
option under "DV Playback"
I chose Medium (deinterlaced).

Now all the streams are fine, and import fine
into DVDSP3.
Too bad this is nowhere in the Manual!

[havema-1]

That's odd. That MPEG Streamclip preference shouldn't have any effect with your problem.

MPEG Streamclip 1.3.1's "DV Playback Quality" preference setting should only affect, erm, the playback quality of the converted DV.

Unlike DV-encoded MOV, the DV streams can't store the playback quality setting in the data fork, but apps like MPEG Streamclip and Toast can store that info in the .dv file's resource fork. The corresponding QT Player settings are:

High (Interlaced): High Quality x, Single Field o, Deinterlace o
Medium (Deinterlaced): High Quality x, Single Field x, Deinterlace o
Low (for very slow Macs): High Quality o, Single Field o, Deinterlace o

With the QuickTime 6 it was a pain to always enable high quality playback so this MPEG Streamclip preference was added.

QT 7 now has a preference for this ("Use high quality video setting when available") so this is somewhat easier now. The only remaining issue is that, even when that QT pref is active, QT 7 Player still doesn't show the full quality if the file itself has some lower quality setting like "deinterlace" enabled.

QuickTime's playback settings DO in some instances have a nasty habit of unexpectedly also affecting the export or import quality to other apps. For example: MediaPipe's mpeg2enc requires the input file's HighQuality playback flag (and no other flag) to be set in order to encode interlaced output (turning interlacing ON in ppmtoy4m and mpeg2enc isn't enough). Also scaling the input file can distort interlacing while exporting etc.

[terryj]

Well havema, I spoke to soon.
Upon simulating the DVD in DVDSP3 BEFORE the final build/burn, the extracted .m2v track starting exhibiting the same blockiness as before, this time starting within two minutes of
playing the track.

I did a test of taking this file ( back to the original MPG)
and making a QT mov from it ( non audio), then I went
back and then hijacked the audio to a new AIFF.
I then ran the audio
through A.pack and got a valid Ac3 file,
and imported the non audio QT Mov and the new audio into
DVDSP3. It plays fine in the viewer, and in simulation, it plays back fine, no blockiness....

There is something in this file that when it gets split the M2v
doesn't perform right. Why encoding it to .mov fixes it
I don't have a clue. Perhaps encoding it to a DV stream
would do the same.

Here is a listing of the general info from MPEG Streamclip:
First the actual file:
Stream: BAWZ_BBSD3.mpg
Type: MPEG program stream

Duration: 2:18:35
Data Size: 1.35 GB
Bit Rate: 1.39 Mbps

Video Tracks:
224 MPEG-1, 352 × 240, 29.97 fps, 1.15 Mbps

Audio Tracks:
192 MP2 stereo, 44.1 kHz, 224 kbps

Stream Files:
BAWZ_BBSD3.mpg (1.35 GB)

then the Elementary streams it creates:
Stream: BAWZ_BBSD3.m2v
Type: MPEG elementary stream

Duration: 2:22:22
Data Size: 2.79 GB
Bit Rate: 2.81 Mbps

Video Tracks:
224 MPEG-1, 352 × 240, 29.97 fps, 1.15 Mbps

Audio Tracks:
160 PCM stereo, 44.1 kHz, 1.41 Mbps

Stream Files:
BAWZ_BBSD3.m2v (1.11 GB)
BAWZ_BBSD3.aiff


also, I checked before exporting to movie, and in Movie Properties, High quality was NOT enabled, and it still played better ( as original MPG, as demuxed from MPEGStreamclip
as m2v, and as QT mov made from original MPG).

So now I'm leaning towards a problem in DVDSP3 at this point.

[sdm]

This problem sounds related to one I reported on apple's discussion board a few months back.

Some update - maybe going from dvdsp2 -> dvdsp3 - or maybe one of apple's 'pro application support' updates caused mpeg1 video files to appear blocky in dvdsp.

I had a project on the go that worked exactly as I expected. I left it alone for a while, then one day continued working on it, and all the video was blocky in the viewer and simulator. I went back to quicktime and looked at the m1v files. They play fine in QT player. I confirmed the problem with many mpeg1 files ... all of which had previously worked properly in dvdsp.

The only answer I got on apple's discussion board was 'your source must be bad' - which it isn't, or 'you can't use mpeg1 video on a dvd' - which you can.

Fortunately I built the dvd anyways, and played it in OSX's dvd player.... it plays fine! I burned the dvd and tested in both my standalone players ... it plays fine!

So it seems dvdsp has developed a problem displaying mpeg-1 video.
No one else has confirmed this for me, but I would like to hear it from someone else.

thanks
-- sdm

[terryj]

Hmm...you bring up some valid points sdm.

If I can work it in this weekend, I will test
burning this off to a DVD-RW, using the
demuxed output, and see how it plays in
my standalones. I know that burning it out
to VCD in original muxed form is ok.