# How does a DVD recorder detect DRM on an Analog video signal?

**URL:** <https://boards.straightdope.com/t/how-does-a-dvd-recorder-detect-drm-on-an-analog-video-signal/576177>\
**Category:** Factual Questions\
**Created:** [March 27, 2011, 7:34pm UTC](https://boards.straightdope.com/t/how-does-a-dvd-recorder-detect-drm-on-an-analog-video-signal/576177 "2011-03-27T19:34:46Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\
**Post date:** [March 27, 2011, 7:34pm UTC](https://boards.straightdope.com/t/how-does-a-dvd-recorder-detect-drm-on-an-analog-video-signal/576177/1 "2011-03-27T19:34:46Z")

</div>

I finally started using a DVD component unit (usually I do all my recording via PC) and was very surprised when I played an Amazon download and hit record on the recorder and it stopped and displayed “COPYRIGHTED CONTENT - CANNOT RECORD” or words to that effect.

I’m using the S-video input which is analog (only digital video-in would be HDMI, right?) so how does the device detect copy protection? I’m not asking for instructions on how to defeat it, I just don’t understand how they’ve plugged the ‘analog hole’ for video.

---

<div class="post-metadata">

**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\
**Post date:** [March 27, 2011, 8:14pm UTC](https://boards.straightdope.com/t/how-does-a-dvd-recorder-detect-drm-on-an-analog-video-signal/576177/2 "2011-03-27T20:14:13Z")

</div>

[Analog Copy Protection.](http://en.wikipedia.org/wiki/Rovi_Corporation#Content_protection_.28RipGuard_and_Analog_Copy_Protection.29) Colloquially known as “Macrovision Protection.”

---

<div class="post-metadata">

**Author:** ![Digital\_Stimulus](https://avatars.discourse-cdn.com/v4/letter/d/aeb1de/32.png) [@Digital\_Stimulus](https://boards.straightdope.com/u/Digital_Stimulus)\
**Post date:** [March 27, 2011, 8:40pm UTC](https://boards.straightdope.com/t/how-does-a-dvd-recorder-detect-drm-on-an-analog-video-signal/576177/3 "2011-03-27T20:40:00Z")

</div>

> [@jz78817](#):
>
> [Analog Copy Protection.](http://en.wikipedia.org/wiki/Rovi_Corporation#Content_protection_.28RipGuard_and_Analog_Copy_Protection.29) Colloquially known as “Macrovision Protection.”

Quoting from that link:

> [@](#):
>
> Macrovision’s legacy analog copy protection (ACP) works by implanting a series of excessive voltage pulses within the offscreen VBI lines of video. These pulses are included physically within pre-existing recordings on VHS, and generated upon playback by a chip in DVD players and digital cable/satellite boxes. A DVD recorder receiving an analog signal featuring these pulses will detect them and display a message saying that the source is “copy-protected”, followed by aborting the recording.

ETA: there may be further methods; ACP is the first mentioned…