Before getting started, you must install the x264 codec in advance. If you do not know how to install it, please refer to the Help section.

Click the Codec menu in oCam, then click the External Codec menu item.

Select Use External Codec, choose the x264vfw codec, and then click the Settings button.

Using the default x264vfw settings as a base, change the parts highlighted in the yellow box in the image below as shown.

The following settings need to be changed. 

Preset - Ultrafast ( Set this to improve encoding speed. The file size may become larger, but if you choose other options, significant lag may occur. )

Profile - High 4:4:4 ( The default profile may cause quality loss, so change it to High 4:4:4 for lossless encoding. )

Keep input colorspace - Keeps the color space of the internally received input buffer.  ( If you use other options, encoding may fail. )

Rate control - Single pass - lossless - Change this for lossless encoding.

Click the OK button to apply the settings.

When recording 64-bit games, the settings are applied to x264vfw64 for 64-bit, so run x264vfw - Configure x264vfw64 from the Start menu and configure it in the same way as shown above.

If you record with the above settings, the video will be recorded losslessly. One important point is that if you want to play back the lossless video without quality loss, you must change the settings in your video player.

Below is how to check a lossless video using PotPlayer.

Run PotPlayer, then click Preferences ( F5 ).

In the Preferences window, 

click Video - Color Space/Attributes on the left, then in the Color Space group box on the right, select Convert manually if possible - Default output color space. ( If you do not configure this, even if the recording is lossless, the screen colors may still be altered during playback. )

Click OK, then play the video recorded losslessly.

At this point, press Ctrl + F1 in PotPlayer. As shown below, the output format of the video codec must be displayed as RGB(32 Bits).

Also, in the playback information under the File Information tab, the following properties must match as shown below.

Format profile                 : High 4:4:4 Predictive@L3

Color space                    : RGB

Color range                    : Full

Matrix coefficients            : RGB

Please note that Windows Media Player does not play this properly, and preview thumbnails will not be displayed in Windows Explorer.