When digitizing composite video from a analog videotape source using the TVP5150's first composite input channel, the captured stream exhibits tearing and synchronization problems[1].
It turns out that commit c0477ad9feca01bd8eff95d7482c33753d05c700 caused "TV mode" (as opposed to "VCR mode" or "auto-detect") to be forcibly enabled for both composite inputs. According to the chip documentation[2], "TV mode" disables a "chrominance trap" input filter, which appears to be necessary for high-quality video capture from an analog videotape source. [ Commit c7c0b34c27bbf0671807e902fbfea6270c8f138d subsequently restricted the problem to the first composite input, apparently inadvertently. ] Since any type of composite signal source can be connected to the TVP5150's first composite input, unconditionally forcing "TV mode" isn't correct. There doesn't appear to be a good way for applications to tell the driver what is connected. Fortunately, the TVP5150 has an operating mode auto-detection feature, which, when enabled, should cause the TVP5150 to auto-detect whether it should use "VCR mode" or "TV mode". Enabling operating mode auto-detection improved video capture quality significantly[3]. Therefore, fix this bug by using operating mode auto-detection. (Also, while here, fix a CodingStyle issue.) For those users who may find this patch via a mailing list archive but who are not able to upgrade to a kernel with a fixed driver: the TVP5150's S-Video and second composite input sources have auto-detection enabled, so you may wish to try using those -- if available on your device -- until this fix makes it a downstream distribution near you. References: 1. Pre-patch tvtime snapshot using a Pinnacle PCTV HD Pro as the capture device and a Sony EV-S2000 as a video source: http://www.booyaka.com/~paul/tvp5150/1a.png 2. Section 3.21.3, "Operation Mode Control Register", _TVP5150AM1 Ultralow-Power NTSC/PAL/SECAM Video Decoder (Rev. D)_ [SLES209D], downloaded 8 October 2010, available via http://focus.ti.com/lit/ds/symlink/tvp5150am1.pdf 3. Post-patch tvtime snapshot (same signal chain as #1, above): http://www.booyaka.com/~paul/tvp5150/1b.png Signed-off-by: Paul Walmsley <p...@booyaka.com> Cc: Hans Verkuil <hverk...@xs4all.nl> Cc: Mauro Carvalho Chehab <mche...@redhat.com> --- drivers/media/video/tvp5150.c | 4 +--- 1 files changed, 1 insertions(+), 3 deletions(-) diff --git a/drivers/media/video/tvp5150.c b/drivers/media/video/tvp5150.c index 1654f65..e4dfb67 100644 --- a/drivers/media/video/tvp5150.c +++ b/drivers/media/video/tvp5150.c @@ -277,7 +277,7 @@ static int tvp5150_log_status(struct v4l2_subdev *sd) static inline void tvp5150_selmux(struct v4l2_subdev *sd) { - int opmode=0; + int opmode = 0; struct tvp5150 *decoder = to_tvp5150(sd); int input = 0; unsigned char val; @@ -290,12 +290,10 @@ static inline void tvp5150_selmux(struct v4l2_subdev *sd) input |= 2; /* fall through */ case TVP5150_COMPOSITE0: - opmode=0x30; /* TV Mode */ break; case TVP5150_SVIDEO: default: input |= 1; - opmode=0; /* Auto Mode */ break; } -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
