Improper Display Aspect Ratio?

[GrouseHiker]

Two different capture methods are apparently producing different DAR's: 4:3 for DV via firewire and 3:2 for Lagarith via s-video.

Before buying a capture card, I experimented with capturing DV via firewire from a Sony DCR-TRV350. MediaInfo shows the following:

Video
ID : 0
Format : DV
Commercial name : DVCPRO
Codec ID : dvsd
Codec ID/Hint : Sony
Duration : 3 min 55 s
Bit rate mode : Constant
Bit rate : 24.4 Mb/s
Width : 720 pixels
Height : 480 pixels
Display aspect ratio : 4:3
Frame rate mode : Constant
Frame rate : 29.970 (30000/1001) FPS
Original frame rate : 29.970 (29970/1000) FPS
Standard : NTSC
Color space : YUV
Chroma subsampling : 4:1:1
Bit depth : 8 bits
Scan type : Interlaced
Scan order : Bottom Field First
Compression mode : Lossy
Bits/(Pixel*Frame) : 2.357
Stream size : 807 MiB (94%)


I just received and installed a Magewell Capture Pro HDMI, which produces the following file characteristics:

Video
ID : 0
Format : Lagarith
Codec ID : LAGS
Duration : 32 s 566 ms
Bit rate : 46.2 Mb/s
Width : 720 pixels
Height : 486 pixels
Display aspect ratio : 3:2
Frame rate : 29.970 (30000/1001) FPS
Standard : NTSC
Color space : YUV
Chroma subsampling : 4:2:2
Bit depth : 8 bits
Bits/(Pixel*Frame) : 4.404
Stream size : 179 MiB (94%)

I have tried various settings, but the output file always shows 3:2 DAR. Also, there is no indication the output file is interlaced.

Do these MediaInfo outputs indicate anything wrong?

By the way, the 486 vertical resolution was an experiment... I assume I should be using 720 x 480.

[DB83]

If memory serves, DV has a proper aspect-ratio flag so your 720*480 displays at 4:3.


Lagarith uses square-pixels so 720*480 is pure 3:2 (do the maths)

[jagabo]

In other words, with Lagarith (and most other lossless codecs) it's up to you to keep track of the display aspect ratio and sample aspect ratio.

[GrouseHiker]

OK - Thanks, so I'm ok on calculated (Lag) vs flagged (DV) DAR. It's up to me to output proper DAR in the final video.

Any way to verify the saved file remains interlaced? I don't see the distinct combing I saw with Windows Media Encoder after capturing the DV videos.

[GrouseHiker]

I found this approach for checking interlacing, but syntax must be wrong... Returns "/dev/null: No such file or directory"

ffmpeg -filter:v idet -frames:v 100 -an -f rawvideo -y /dev/null -i [filename]

[jagabo]

That's linux syntax. For windows you can use:

ffmpeg -i filename.avi -filter:v idet -frames:v 100 -an -f null -

Or open your video in VirtualDub2 and look at it in the input pane. You should see comb artifacts if it's interlaced.

[GrouseHiker]

That's linux syntax. For windows you can use:

ffmpeg -i filename.avi -filter:v idet -frames:v 100 -an -f null -

Or open your video in VirtualDub2 and look at it in the input pane. You should see comb artifacts if it's interlaced.

Thanks!! As I suspected (based on viewing), the s-video captured file is not interlaced:
[Parsed_idet_0 @ 0000023ad9a7cf00] Single frame detection: TFF: 0 BFF: 0 Progressive: 100 Undetermined: 1
[Parsed_idet_0 @ 0000023ad9a7cf00] Multi frame detection: TFF: 0 BFF: 0 Progressive: 100 Undetermined: 1

Now, I've just got to figure out why...

[GrouseHiker]

I'm going to start a new thread, since I've deviated from the original DAR question. Thanks for the help!

[jagabo]

Keep in mind that that command only looks at the first 100 frames. If your video starts with a still shot the report may not be accurate.