Panasonic recommends Class 6 or higher SD cards for capturing HD video with GH1 and GF1 cameras. However, many users have reported success with recording videos on Class 6 cards at far higher bitrates than the maximum 17Mbps supported by the unpatched MJPEG encoder. In the course of developing my 35Mbps MJPEG In-Camera Playback Patch, I experimented with bitrates well over 50Mbps, though of course videos with such high bitrates would not play back in camera. (More details here: http://www.dvxuser.com/V6/showthread.php?t=215624 )
High bitrates can deliver near flawless MJPEG image quality, and in situations where in-camera playback is not required, obtaining maximum usable bitrates from Class 6 SD cards is highly desirable. Unfortunately, it has been difficult to identify reliable MJPEG settings that are safe from sporatic and unpredictable recording errors.
Fortunately, Tom's Hardware recently completed performance tests of a wide range of SD cards, from Class 4 to Class 10. The results of their record speed tests can be found here:
http://media.bestofmicro.com/F/F/178107/original/sdhc-transfer-write.png
The slowest of the Class 6 cards had a minimum write speed of 8.4MBytes per second, equal to 67Mbps. Reserving a 10% headroom margin for safety, I concluded that Class 6 SD cards should be capable of recording video at a mean bitrate of 60Mbps.
In order for a high bitrate to deliver superior image quality, the quantization tables used by the MJPEG encoder must record fine-grain details with a high degree of precision. Recent research lead by modulr has shown that JPEG Quality Levels up to 100 can be achieved with Class 10 SD card bitrates over 70Mbps:
http://dvxuser.com/V6/showthread.php?t=215785
A number of JPEG image quality studies have shown, however, that Quality Levels above 95 are rarely distinguishable from the original image:
http://en.wikipedia.org/wiki/JPEG#Sample_photographs
JPEG Quality Levels approaching 100 are especially desirable for preserving subtle details in low-light images. In my experience, with well-lit, complex scenes, Quality Level 90 and above produces near flawless images, even at high magnification. In order to produce optimal bitrates for low-light images, the Quality Levels of highly detailed images must be constrained to keep their bitrates below 65Mbps.
After some experimentation, I've arrived at the following MJPEG patch settings for 720p @ 30fps in 4:2:2 color mode. This has consistently produced images with Quality Level 90-100 at bitrates very close to 60Mbps:
On the AVCHD side, I've paired this 60Mbps MJPEG Class 6 SD Card Patch with my 50Mbps AVCHD 3-Frame GOP Patch:
http://dvxuser.com/V6/showthread.php?t=222791
High bitrates can deliver near flawless MJPEG image quality, and in situations where in-camera playback is not required, obtaining maximum usable bitrates from Class 6 SD cards is highly desirable. Unfortunately, it has been difficult to identify reliable MJPEG settings that are safe from sporatic and unpredictable recording errors.
Fortunately, Tom's Hardware recently completed performance tests of a wide range of SD cards, from Class 4 to Class 10. The results of their record speed tests can be found here:
http://media.bestofmicro.com/F/F/178107/original/sdhc-transfer-write.png
The slowest of the Class 6 cards had a minimum write speed of 8.4MBytes per second, equal to 67Mbps. Reserving a 10% headroom margin for safety, I concluded that Class 6 SD cards should be capable of recording video at a mean bitrate of 60Mbps.
In order for a high bitrate to deliver superior image quality, the quantization tables used by the MJPEG encoder must record fine-grain details with a high degree of precision. Recent research lead by modulr has shown that JPEG Quality Levels up to 100 can be achieved with Class 10 SD card bitrates over 70Mbps:
http://dvxuser.com/V6/showthread.php?t=215785
A number of JPEG image quality studies have shown, however, that Quality Levels above 95 are rarely distinguishable from the original image:
http://en.wikipedia.org/wiki/JPEG#Sample_photographs
JPEG Quality Levels approaching 100 are especially desirable for preserving subtle details in low-light images. In my experience, with well-lit, complex scenes, Quality Level 90 and above produces near flawless images, even at high magnification. In order to produce optimal bitrates for low-light images, the Quality Levels of highly detailed images must be constrained to keep their bitrates below 65Mbps.
After some experimentation, I've arrived at the following MJPEG patch settings for 720p @ 30fps in 4:2:2 color mode. This has consistently produced images with Quality Level 90-100 at bitrates very close to 60Mbps:
- MJPEG E1 Quality = 280
- MJPEG E1 Table = 4
- MJPEG E2 Quality = 250
- MJPEG E2 Table = 10
- MJPEG E3 Quality = 225
- MJPEG E3 Table = 24
- MJPEG E4 Quality = 200
- MJPEG E4 Table = 48
On the AVCHD side, I've paired this 60Mbps MJPEG Class 6 SD Card Patch with my 50Mbps AVCHD 3-Frame GOP Patch:
http://dvxuser.com/V6/showthread.php?t=222791
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