-fast option suppresses unexpected tags

Started by Mac2, August 28, 2016, 08:10:42 AM

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Mac2

August 28, 2016, 08:10:42 AM
Version: ExifTool 10.25 on Windows (current version).

I just had a support case where some M2TS data from a .M2TS video file were not imported by my application.
Doing a quick

exiftoo.exe -G -all:all --system:all --file:all test.m2ts

shows

ExifTool]      ExifTool Version Number         : 10.25
[M2TS]          Video Stream Type               : H.264 Video
[M2TS]          Audio Stream Type               : SDDS Audio
[M2TS]          Audio Bitrate                   : 640 kbps
[M2TS]          Surround Mode                   : Not indicated
[M2TS]          Audio Channels                  : 3/2
[H264]          Image Width                     : 1920
[H264]          Image Height                    : 1080
[M2TS]          Duration                        : 0:01:03
[Composite]     Image Size                      : 1920x1080
[Composite]     Megapixels                      : 2.1

My software uses the -fast option in addition by default, and in this case, the Duration tag is not included in the result.
I assume that calculating this tag is considered 'slow' on large files or maybe files on remote storage? I could not tell a difference for a 100 MB file on a local SSD though.

Is there a list somewhere or a command to find out which other tags are suppressed when fast is used?
I thought this was only relevant for JPEG files.

Phil Harvey

#1
August 28, 2016, 11:14:58 AM
The best documentation for this is the FastScan API option documentation, but it doesn't mention what specific tags are dropped.

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux/PowerShell, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

Mac2

#2
August 28, 2016, 12:08:15 PM
Thanks, Phil.

That's more info than in the command line docs, but as you said, only a rough description of tags maybe skipped.

I have disabled -fast option in my application and I will check for feedback when the new version comes out and users work with it. I doubt that it will cause any noticeable performance degradation. I've made a few tests but I could not see any difference for image formats, including large JPEG or RAW files. And video files are slow to process anyway, the time used by ExifTool to extract the metadata is only the tip of the iceberg anyway   ;)

Have a nice weekend. And, as always, thank you for ExifTool  :D
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