But if the EDID incorrectly says the device will receive, say,
compressed formats like Dolby’s AC-3, and this fact hasn’t
been tested or brought up at a PlugFest, the first people to find
out might be the manufacturer’s customers. These days, when
disgruntled users can rapidly make their displeasure regarding
an apparently dysfunctional machine heard around the world via
consumer forums, it’s much better for manufacturers if such problems
never make their way into the public domain.
Ideally, HDMI- and EDID-related problems should be picked
up at the R&D stage of the product’s development, rather than at
a PlugFest before the scrutiny of the world’s HDMI manufacturers,
or when the device is already on the production line. There’s
sense in using PlugFests in addition to a carefully designed inhouse
program of rigorous product testing.
Sill, a few ad hoc interconnection tests performed on some preproduction
hardware at a PlugFest can’t be considered a replacement
for proper product testing programs. Using accurate EDID
information, and a thorough program of audio and video testing at
the design stage, can nip these problems in the bud.
SPECIFIC RECOMMENDATIONS
Manufacturer-led support for accurate EDID is good news for
both customers and manufacturers. Use of off-the-shelf EDIDs
should be avoided. Also, the product design team, which needs to
be trained properly in the art of writing properly specified EDID
information, should create it so it properly describes the capabilities
of the specific product—and not just one in that range.
The device should then be given to an EDID-conversant test
engineer, ideally someone not involved with the product design,
who should decompile the EDID. This is not as hard as it sounds.
Plenty of companies such as Audio Precision make devices capable
of reading and editing EDID.
But just reading the EDID isn’t enough. The engineer also
needs to test the device’s ability to cope with the media formats
that the onboard EDID says it can handle. Again, this isn’t difficult.
It’s simply a matter of constructing a systematic test program
that involves firing these media types—including obscure
HD video and compressed audio formats where necessary—at
the device under test and evaluating the results. Error handling
should also be tested. This would be done by sending deliberately
corrupted information and seeing exactly how the device handles
data that the EDID says is untenable.
With modern video and audio test hardware, the process of testing,
analysis, and results reporting can be automated and integrated
into a software-based process control environment. In this way,
any problems with the EDID or with the device’s ability to behave
according to its advertised specification could be picked up long
before the product reaches end users. None of this needs to
replace testing sessions at the likes of PlugFest, but it might make
for more reliable HDMI equipment at both the broadcast and consumer
level.