Hi Hans, On Sat, Jun 20, 2009 at 03:05:24PM +0200, ext Hans Verkuil wrote: > Hi all, > > Besides the new RDS controls implemented by Eduardo we also need a few > additions to the V4L2 API. > > First of all we need two new capabilities for struct v4l2_capability: > > #define V4L2_CAP_RDS_OUTPUT 0x0000800 /* Is an RDS encoder */ > #define V4L2_CAP_MODULATOR 0x0008000 /* has a modulator */ > > The current V4L2 spec says in section 1.6.2 that you should set > V4L2_CAP_TUNER when you have a modulator. I see absolutely no reason why we > shouldn't add a proper CAP_MODULATOR instead. Almost all caps already come > in an input and output variant, so it also makes sense to have a tuner and > a separate modulator capability. Since Eduardo's FM transmitter is the > first driver with a modulator that will go into the tree we do not have to > worry about backwards compatibility, so I think we should fix this weird > rule. > > For the same reason we should add an RDS_OUTPUT capability since not all FM > transmitters might have a RDS encoder. Again, this is also consistent with > the V4L2_CAP_RDS_CAPTURE capability that we already have. > > The RDS decoder API adds a new v4l2_tuner RDS capability and RDS subchannel > flag. These are reused in v4l2_modulator. If the RDS capability is set, > then the modulator can encode RDS. If the V4L2_TUNER_SUB_RDS channel is > specified in txsubchans, then the transmitter will turn on the RDS encoder, > otherwise it is turned off. This is consistent with the way txsubchans is > used for the audio modulation. > > Eduardo, this will replace the RDS_TX_ENABLED control, so if this goes in > then that control has to be removed. I like this approach. Looks cleaner. How about moving some of the *_ENABLED features from FM TX class to a CAP flag? As you are proposing for RDS? I mean, some of them are consistent with audio modulation (copying from my patch): +#define V4L2_CID_RDS_TX_ENABLED (V4L2_CID_FM_TX_CLASS_BASE + 1) This one you are already proposing to move to a CAP flag. +#define V4L2_CID_AUDIO_LIMITER_ENABLED (V4L2_CID_FM_TX_CLASS_BASE + 6) This is relevant to modulators which apply some sort of dynamic audio control to maximize audio volume and minimize receiver-generated distortion. Also important to prevent audio over-modulation. +#define V4L2_CID_AUDIO_COMPRESSION_ENABLED (V4L2_CID_FM_TX_CLASS_BASE + 9) Enables or disables the audio compression feature. This feature amplifies signals below the threshold by a fixed gain and compresses audio signals above the threshold by the ratio of Threshold/(Gain + Threshold). + +#define V4L2_CID_PILOT_TONE_ENABLED (V4L2_CID_FM_TX_CLASS_BASE + 14) Some modulator generates pilot tone in audio channel. I mean, what do you think to have those as a flag in txsubchans instead of a separated ext control ? > > I've made a first implementation of these changes in this tree: > http://linuxtv.org/hg/~hverkuil/v4l-dvb-rds-enc > > This tree also contains the RDS decoder changes from my v4l-dvb-rds tree > since it needs to build on those. > > Comments? > > Regards, > > Hans > > -- > Hans Verkuil - video4linux developer - sponsored by TANDBERG Telecom -- Eduardo Valentin -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
