Hi Hartmut, Ricardo, Dmitri, (hopefully I have the right addresses, if not - sorry for bothering :-))
Hermann recommended me to contact you for this issue. I would like to ask you if any of you (or any other reader!) is working on saa7134-alsa or saa7134-tvaudio or have any plans to do so. Also if you find any section below interresting, please comment it. I'm seeking for opinions from anybody who has more knowledge in saa713x audio programming than me :-) My main concern is that ALSA reports wrong frequency for TV (48kHz) while it can use only 32kHz, second is the correct setting up of 48kHz for LINE1/LINE2 (doesn't work at the moment). There are possibly also other concerns - ALSA controls update for example. My plan is to come up with few patches after the discussion for another discussion. On Monday 13 of July 2009 at 21:20:38, Oldrich Jedlicka wrote: > Hi Hermann, > > On Monday 13 of July 2009 at 03:06:41, hermann pitton wrote: > > Hi Oldřich, > > > > this needs to be looked up during day time, preferably with the register > > settings for all involved saa713x devices, which I do not have ... > > You can respond the next day, no need to stay awake :-) > > > Am Sonntag, den 12.07.2009, 19:48 +0200 schrieb Oldřich Jedlička: > > > Hi all, > > > > > > I had a look at the audio code in saa7134 directory once again > > > (saa7134-alsa.c and saa7134-tvaudio.c). It has one major problem - the > > > frequency for SAA7134 isn't set during startup, only during the capture > > > source change (that is another problem). But let's start from > > > beginning, please comment what you find interresting, I will create a > > > patch after the discussion for another discussion :-). > > > > ;) > > > > > 1. SAA7133/SAA7135 > > > > > > SAA7133/SAA7135 always use DDEP (DemDec Easy Programming) mode which > > > runs on 32kHz only. There is no need to change the frequency at all, so > > > everything works except that the info coming from ALSA reports both > > > frequencies 32kHz and 48kHz as available for recording. This can be > > > easily changed in snd_card_saa7134_hw_params to report only 32kHz for > > > SAA7133/SAA7135. > > > > So, for now, agreed. But you should try to talk to Ricardo and Hartmut > > in this case. I can tell you about the three years it did not work. > > Do you mean Ricardo Carrillo Cruz and Hartmut Hackmann? I've found them via > Google (Google knows everyone :-)) I can add them to CC. Do you know if > they are still working on the code (saa7134-tvaudio, saa7134-alsa)? > > > > 2. SAA7134 > > > > > > SAA7134 is special in the way it programs the frequency by hand. It > > > uses 32kHz DemDec mode for TV (DemDec works only in 32kHz mode), 32kHz > > > for radio (this is locked), and 32kHz/48kHz for S-Video and Composite > > > inputs. ALSA again reports both frequencies 32kHz and 48kHz as > > > available for recording - this can be changed accordingly. > > > > Agreed. > > > > > The problem is that the frequency is never changed during > > > inicialization like it was in OSS code (see 2.6.24 kernel, > > > saa7134_oss_init1 calls mixer_recsrc). I think that this responsibility > > > is now on the > > > snd_card_saa7134_capture_prepare method - it should set the frequency > > > in SAA7134_SIF_SAMPLE_FREQ register correctly, possibly also > > > SAA7134_ANALOG_IO_SELECT. Note that the tvaudio's mute_input_7134 sets > > > the frequency to 32kHz, this can be thrown away I think. > > > > Agreed. If any, that is the only "regression" to report compared to > > saa7134-oss. > > > > > I tried to set SAA7134_SIF_SAMPLE_FREQ in > > > snd_card_saa7134_capture_prepare and the capturing works correctly with > > > 48kHz from my digital camera (Composite input). > > > > OK, that should be previous behaviour then. > > > > > 3. Changing the capture source > > > > > > The ALSA interface has three capture sources, all of them have left and > > > right channels (boolean values) - LINE1, LINE2 and TV. The user can > > > select any source - ALSA calls snd_saa7134_capsrc_put. > > > > Note, without looking any further, LINE1 and LINE2 are left/right > > _pairs_ of stereo inputs. In saa7134-oss it was needed to select them > > card specific. > > I understand that they are left/right pairs. The saa7134-oss code knew > about TV, LINE1, LINE2 and LINE2_LEFT possibilities. The LINE2_LEFT worked > only on SAA7134 chip, because it programmed the OCS (output crossbar > select) to record LINE2's left channel only. I don't see anything special > in 2.6.24 kernel in saa7134-oss.c for setting the LINE1/LINE2/LINE2_LEFT in > a card specific manner (other than SAA7133/34/35). Moreover, the _correct_ > output channel selection for LINE2_LEFT wasn't done in saa7134-oss code, > but in saa7134-tvaudio (which is a little bit strange). > > The biggest problem - when I read the specification that I've found years > ago - is that I don't know which registers can be changed in the DDEP mode. > Maybe it would be possible to enable the _real_ left/right-only channel > selection for all SAA713x chips. > > > > The ALSA controls are not updated, so it is possible to select both > > > LINE1 and LINE2 at the same time, but recording will use only one of > > > them - the last changed control wins. Moreover the left/right selection > > > doesn't make any difference, the code ignores it. > > > > For saa7133/35/31e that was exactly Hartmut's plan. You don't have to > > care to select the right inputs anymore. And with Ricardo exporting the > > mute symbol from saa7134-tvaudio to saa7134-alsa, you don't have to care > > for this either. (mythtv v4l1, except you do ambiguous stuff from user > > side) > > The just-works is good and it would be good to automatically update the > ALSA capture source (the control) when the application opens/selects the > corresponding v4l device. I actually don't know how, but I can learn > (Google is our friend) :-) > > > > Here comes also the frequency problem of SAA7134. If the user starts > > > with LINE1 and 48kHz and tries to switch to TV, the frequency will > > > change to 32kHz (DemDec mode) - the application will not know, I guess > > > there will be some buffer underruns. > > > > Anyway, to switch to 32kHz for TV is right currently, but it doesn't > > stop since years, that it is claimed, more is possible. No proof for any > > standard yet and A2 and NICAM won't do at least. > > When the driver switches to different frequency, the application will still > play in the original rate. This means that the 32kHz data will be played at > 48kHz, so the application will play each captured block at higher frequency > with pauses in between. This doesn't sound good, this should be disallowed > somehow when the recording is ongoing. Or is it possible to send > configuration update to ALSA system about the fact that the source > frequency has changed? > > Another thing is which frequencies the driver should report to ALSA? When > you change the capture source (either by the v4l interface or by the mixer > controls), the capabilities change too. This is another argument agains the > 48kHz I think. > > > > Note that any change of capture source control is overriden by the call > > > to snd_card_saa7134_capture_prepare (called by ALSA before the capture > > > source is opened) that takes the current input as set by > > > saa7134_tvaudio_setinput (called by v4l interface). I think this is > > > actually expected behaviour and can stay as it is now. > > > > There are also cards with mpeg encoders and you can't just mute or do > > what you want. > > > > > The easiest solution would be to throw away the capture source control > > > and let the capture source initialization on the > > > snd_card_saa7134_capture_prepare method (the source would be controlled > > > by saa7134_tvaudio_setinput only - through v4l interface only), or > > > limit the frequency to 32kHz only so that any source can be freely > > > selected on any SAA713x hardware. > > > > I'm not sure, in case we are talking about all sources, talk about the > > same things already. Also, you might have noticed or not, there are also > > mute calls depending on having a signal. > > That's right, the saa7134-tvaudio has a thread to check the signal/stereo > (when the TV source is selected) and it also has a more complete source > channel control (than the one found in saa7134-alsa/oss). It also changes > the frequency to 32kHz when the LINE1/LINE2 are used... I think this should > be changed somehow to have the channel configuration at one place (not in > both saa7134-tvaudio's mute methods and in saa7134-alsa). > > > > Any other ideas, comments, corrections (I could be wrong in what I > > > wrote, I'm not the SAA713x programming expert!), suggestions? > > > > > > Cheers, > > > Oldrich. > > > > Given the problems we had previously, I'm not right sure, if we really > > have some now at all, hm, 02:52 am ;) > > > :-) > : > > But you have at least some reaction ... > > > > Cheers, > > Hermann > > Thanks for your comments, Hermann. > > Cheers, > Oldřich. Cheers, Oldřich. -- 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
