On https://web.archive.org/web/20090318021921/http://club.cdfreaks.com/f52/offsets-handling-syncing-audio-data-vs-q-channel-111913/#post726955 https://web.archi

On https://web.archive.org/web/20090318021921/http://club.cdfreaks.com/f52/offsets-handling-syncing-audio-data-vs-q-channel-111913/#post726955 https://web.archive.org/web/20090318021921/http://club.cdfre... someone writes: 'I used an oscilloscope to find a sweet spot in the analog signal path of an audio CD player (an old Sanyo - the older the better, for this kind of stuff...) where a pre-filtered and amplified version of the laser readout is available - in this particular player, this is basically a test header marked "EFM" (which provides a good hint to its function - it's the last analog stage of the signal, just prior to entering the digital Fourteen-to-Eight demodulator). This point is probed and fed into a high-speed AD converter (12 bit res, 50 Msamples/sec) that is hooked to an FPGA. I implemented a flank detector and a run-length encoder in VHDL.' And later in the thread: 'Old audio CD players are so amazingly stupid, they will happily "play" CD-ROM discs if you feed it with one. This is truly ideal for analysis purposes.'