The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Category: Photography & Images

Taking & making images.

Sony HDR-AS30V vs. ExFAT vs. Ext2 Times: Total Bafflement
I’d like to overlay a timestamp on still images extracted from Sony HDR-AS30V camera videos, ideally including the frame number, to record exactly when the incident occurred. Movie players use relative time, with 00:00:00 at the beginning of the file, so we’ll need either the file timestamp or the timestamp recorded in the image’s Exif data, plus the frame number modulo 60 (or, shudder, 59.94 for NTSC).

The ExFAT format used on 64 GB MicroSD cards stores the file’s creation time, its modification time (writing data), and the most recent access time (reading data). That’s similar to the Linux ext2/3/4 filesystem time and unlike plain old FAT, which omits the access time.

The various FAT formats store local time, with no regard for time zones, Daylight Saving Time, or anything else. Linux stores times as UTC and converts to local time on the fly. This has catastrophic consequences for getting any of this right.

It helps to have alias ls='ls -h --color=auto --time-style=long-iso' in your .bashrc file.

The HDR-AS30V has a year-month-day calendar, a 24-hour clock, a Time Zone value, and a separate DST on/off setting.

Turning DST on adds 1 hr to the Time Zone value, turning it off subtracts 1 hr. That has the side effect of changing the clock time: not what I expected. You must, therefore, set the TZ first, then DST, then the clock, which does not follow the menu’s natural order of things.

The camera sets file timestamps as it creates the files, but Linux also meddles with the values while displaying them. Some doc suggests that Linux regards FAT file timestamps as UTC and applies DST correction, which seems to match what I see. There’s a mount option (-o tz=UTC) that seems to have no effect, as well as an undocumented time offset (-o time_offset=60) that also has no effect.

Setting the TZ to GMT+0 (Sony uses GMT, not UTC) for simplicity, setting the clock to the correct local time, and twiddling DST shows that:
- Rebooting (remove /insert battery) doesn’t change anything
- Metadata in file = clock setting – DST setting (-1 on, +0 off)
- MP4 / THM file create / modify times = always clock +1 hour
- MP4 / THM file access times = as create / modify until next Linux access
Under those conditions, with the clock set to (locally accurate) 1908, UTC+1, and DST off, then the Exif timestamp metadata for a movie created at that time look like this:
```
exiftool /mnt/part/MP_ROOT/100ANV01/MAH00036.MP4 | grep -i date
File Modification Date/Time     : 2014:09:01 20:08:09-04:00
File Access Date/Time           : 2014:09:01 19:10:14-04:00
File Inode Change Date/Time     : 2014:09:01 20:08:09-04:00
Create Date                     : 2014:09:01 19:08:03
Modify Date                     : 2014:09:01 19:08:08
Track Create Date               : 2014:09:01 19:08:03
Track Modify Date               : 2014:09:01 19:08:08
Media Create Date               : 2014:09:01 19:08:03
Media Modify Date               : 2014:09:01 19:08:08
```
The corresponding filesystem values:
```
ll /mnt/part/MP_ROOT/100ANV01/
total 146M
... snippage ...
-rwxr-xr-x 1 ed root  14M 2014-09-01 20:08 MAH00036.MP4
-rwxr-xr-x 1 ed root 8.5K 2014-09-01 20:08 MAH00036.THM

ll -c /mnt/part/MP_ROOT/100ANV01/
total 146M
... snippage ...
-rwxr-xr-x 1 ed root  14M 2014-09-01 20:08 MAH00036.MP4
-rwxr-xr-x 1 ed root 8.5K 2014-09-01 20:08 MAH00036.THM

ll -u /mnt/part/MP_ROOT/100ANV01/
total 146M
... snippage ...
-rwxr-xr-x 1 ed root  14M 2014-09-01 19:10 MAH00036.MP4
-rwxr-xr-x 1 ed root 8.5K 2014-09-01 20:08 MAH00036.THM
```
The THM file contains a 160×120 pixel JPG thumbnail image taken from the first frame of the corresponding MP4 file. For longer movies, it’s more obvious that the MP4 file creation date is the start of the movie and its modification date is the end. The maximum 4 GB file size of corresponds to exactly 22:43 of 1920×1080 movie @ 60 frame/sec (the metadata says 59.94).

The +1 hour offset in the file create / modify times comes from the FAT timestamp being (incorrectly) adjusted by the Linux DST setting. When exiftool reads the MP4 file, that resets its access time to the actual time as seen by Linux, thereby crushing the bogus FAT time.

Doing the seemingly sensible thing of setting the camera to have the correct local time (roughly 1930), the correct time zone, and the correct DST setting produces this jumble:
```
exiftool /mnt/part/MP_ROOT/100ANV01/MAH00037.MP4 | grep -i date
File Modification Date/Time     : 2014:09:01 20:33:15-04:00
File Access Date/Time           : 2014:09:01 20:33:14-04:00
File Inode Change Date/Time     : 2014:09:01 20:33:15-04:00
Create Date                     : 2014:09:01 23:33:11
Modify Date                     : 2014:09:01 23:33:14
Track Create Date               : 2014:09:01 23:33:11
Track Modify Date               : 2014:09:01 23:33:14
Media Create Date               : 2014:09:01 23:33:11
Media Modify Date               : 2014:09:01 23:33:14

ll /mnt/part/MP_ROOT/100ANV01/MAH00037*
-rwxr-xr-x 1 ed root  11M 2014-09-01 20:33 /mnt/part/MP_ROOT/100ANV01/MAH00037.MP4
-rwxr-xr-x 1 ed root 8.2K 2014-09-01 20:33 /mnt/part/MP_ROOT/100ANV01/MAH00037.THM

ll -c /mnt/part/MP_ROOT/100ANV01/MAH00037*
-rwxr-xr-x 1 ed root  11M 2014-09-01 20:33 /mnt/part/MP_ROOT/100ANV01/MAH00037.MP4
-rwxr-xr-x 1 ed root 8.2K 2014-09-01 20:33 /mnt/part/MP_ROOT/100ANV01/MAH00037.THM

ll -u /mnt/part/MP_ROOT/100ANV01/MAH00037*
-rwxr-xr-x 1 ed root  11M 2014-09-01 19:34 /mnt/part/MP_ROOT/100ANV01/MAH00037.MP4
-rwxr-xr-x 1 ed root 8.2K 2014-09-01 20:33 /mnt/part/MP_ROOT/100ANV01/MAH00037.THM
```
The only correct time in that mess is in the next-to-last line: the access time for the MP4 file. Every other timestamp comes out wrong, with the internal metadata values being off by +4 hours; that suggests the camera sets the internal timestamps to UTC.

As nearly as I can figure, the only way to make this work requires setting the clock to the local time, TZ to UTC+0, and DST off. That will screw up the filesystem timestamps, but at least the Exif metadata will be correct, for some value of correct.

The camera’s GPS receiver depends on the clock for its initial synchronization. I don’t know how the TZ and DST settings affect the clock’s correctness for that purpose.

I do not know if / how / when the displayed times have been altered by the programs that display them.

I think exiftool can extract the times from the internal metadata and fix up the filesystem times, but that’ll take more tinkering.

Sheesh & similar remarks…
2014-09-02
Milkweed Tussock Moth

Although we no longer see Monarch butterflies, our milkweed patch attracts Milkweed Tussock Moth caterpillars:

Milkweed Tussock Caterpillar

This one apparently died on the patio step, half the house away from the milkweed patch, and the rear spines (on the right) have begun falling out. During the next week, I teleported two more from that step to the patch, under the assumption they’d be happier on a tasty leaf than on a slate slab.

They were all early instars, very short and quite fuzzy. Later instars will be much longer, with more distinct tussocks.

I wonder if you could shear them and use the “fur” for decoration? It wouldn’t spin into thread like wool, but someone, somewhere, has surely performed art with Tussock Caterpillar spines…

2014-08-31
Real Estate Sale Signage

Real Estate Agencies used to post property marker signs like this:

FSReEx-168

Even far off to the side, a bright background color catches your eye:

FSWeRe-107

The signs sported primary colors, reasonably large type, and simple words, making them almost readable in those pictures and definitely legible from the driver’s seat. While not particularly handsome or stylin’, they got the message across: this house is for sale.

Then a strange thing happened.

Berkshire Hathaway somehow got into the real estate business and Borged several of the local agencies. BH being a Name Brand with a connotation of wealth & taste, their branding imposed a subtle touch on the new signage:

FSBkHath-113

No, you can’t quite read that in real life, either, although the agent’s name and number on the header come close to the old standard.

One day, a old-school sign appeared along one of our usual routes:

FSHoLa-127

Although white and green don’t pop out of the background, the sign has enough contrast that you can read what’s needed.

Then they became affiliated with Christie’s, the Big Name in the realm of high-end auctions. I have no idea what Christie’s has to do with real estate, but if Berkshire Hathaway can do it, it seems Christie’s thinks they can do it even better.

In any event, the Christie’s Corporate Standard evidently calls for very, very subtle signage:

That sign might mark a high-end bed and breakfast, but certainly does not tell me that the place is for sale: none of the text approaches readability from the street, certainly not at normal travel speeds, and nothing about it even suggests that I should take action.

A few weeks later, two hang tags added a COMMERCIAL note (the property evidently has potential to become an office or retail space) and the agent’s name and phone number in minuscule type:

FSBase-128

After a while, a very bright red do-it-yourself HOUSE FOR SALE placard suggested the property owner wasn’t entirely satisfied with the results to date:

FSSign-148

The high-contrast black-on-white FOR SALE header definitely doesn’t match the rest of the sign, but its more legible information might motivate you to pause and puzzle out the rest. The red placard vanished a few days after the header appeared, leaving us with this peculiar mix:

FSHeader-153

None of the (numerous) Christie’s signs in the area have a header, so this may be a case of a squeaky wheel getting greased. I won’t be surprised to see a corporate image change, including larger type, as these fancy signs weather away.

Perhaps the correct conclusion to be drawn is that, in this Internet age, nobody buys a house based on the quaint custom of driving by a house-with-sign, thinking “Hey, that’s perfect for me!”, and calling the agent, so there’s no need for anything more than a pro-forma marker identifying a property that will be selected by filters applied to MLS / Zillow databases.

The most recent change simplifies the sign to the bare minimum:

FSMissing

Perhaps we’ve witnessed a falling-out over typography?

This began as a test of the Sony HDR-AS30V camera’s resolution, with the obvious conclusion it wasn’t intended as a camera suitable for recording text.

2014-08-30
NP-BX1 Lithium Batteries: 6 Month Status

The battery capacities after six months are, of course, lower:

Sony NP-BX1 – OEM Wasabi – 2014-08-17

I didn’t bring the HDR-AS30V camera along on the Hudson River ride, simply because each battery lasts about 1.5 hr in 1920×1080 @ 60 fps mode and I wasn’t up to replacing batteries during the ride, then charging all three every evening. Obviously, the camera wasn’t intended for that use case.

Somewhat surprisingly, the Wasabi batteries deliver the same continuous run time as the Sony battery: 1:30 vs 1:33. I used 250 mA for those discharge curves, but I think something around 500 mA would better match the camera load.

I’m sorely tempted to drill a hole in the camera’s case and wire in a honkin’ big prismatic lithium cell.

2014-08-25
Cycling the Hudson Valley: 2014

Seven days and 300 miles of pedal pushing:

KE4ZNU route – 2014-07-28 through 2014-08-04

We rode north to the start of the Cycling the Hudson Valley ride in (wait for it) Hudson, rode south while crossing the Hudson six times, then I rode north from Da Bronx while the other 100 riders proceeded south to the tip of Manhattan and the finish line in Brooklyn. Mary, alas, drove the last few days to avoid aggravating a tender tendon.

While everybody else had a touristing day in Hyde Park, we slept in our own beds for two nights.

Everything you need to know about modern bicycle touring:

Cycling the Hudson Valley – Charging Station

The straight line along the right side of the map, from just below the New Croton Reservoir to Hopewell Junction, represents data loss from riding in a valley, plus knocking the coaxial power plug out of the battery pack where the South County Trail becomes one with Rt 100 / Saw Mill River Road for a few miles.

That last day had plenty of hillclimbing, even on the rail trail, but with a rewarding section of Rt 52 that drops 500 feet in a mile; I hit 41 mph while passing under I-84.

A good time was had by all!

2014-08-19
Clymene Moth

The first Clymene Moth we ever saw:

Clymene Moth

It’s a poor picture, but the moth was up and away after that; as always, the poor picture you get is better than the great picture you might have gotten.

A few days later, we spotted two of them on a brick wall, so there must be a bunch more out there.

2014-08-17
Monthly Image: Overblown Vette

I should do something like this to the Forester:

Seriously Blown Vette

We were volunteering at the annual Locust Grove Classic Car Show, which also included a monster 1913 FIAT made in Poughkeepise.

2014-08-15