Roger: When you're using an HVR-1950 - actually *ANY* tuner to perform ATSC capture - you're not really "capturing" anything in the traditional sense. Unlike old analog video where the broadcast format uses "pre-digital age" separately modulated analog video and audio, when you're grabbing ATSC all you are doing is grabbing a bit stream from the broadcast station. Nothing more. The "tuner" in this case is very very simple - all it has to do is demodulate the station's carrier to recover the bit stream. The tuner actually doesn't have to care at all what is inside that bit stream - that's "somebody else's problem...". All timing information is part of that bit stream, and audio vs video data within it is just subpackets in the container format. In fact, ATSC data is really just MPEG container format with just some additional rules applied.
The HVR-1950 tuner when run in ATSC mode just grabs the bits and all the pvrusb2 driver does is hand the bits off to the DVB core (which then does further processing on the bit stream to select out specific subchannel data packets from the overall data flow). So if you have issues of audio / video sync, or problems with frame synchronization, it really can't be caused by the tuner or the driver. In fact the only possible scenario here is if the received signal is too weak then the demodulated bit stream could have dropouts / corruption in it - but that would be true for any tuner setup. The previous audio / video sync issues you are refering to from a long time ago would have had to do with analog capture, which is completely different. In that case, the hardware is quite a bit more complicated, since it has to separately recover the video & audio signals, render the video into frames and then encode all of it merged to mpeg for delivery to the application. None of those steps happen with ATSC since the transport data received is already mpeg data. ATSC video tuners are actually simpler than analog tuners. Happy holidays, -Mike On Mon, 24 Dec 2012, Roger wrote: > > >> Think I'm running into an issue with streams created by the pvrusb2 > >> driver, or > >> Hauppauge devices. > >> > >> Avidemux seems to loose sync, even after manually specifying NTSC (~29 > >> fps). > >> On initial import of the video, the FPS is set to an initial >50 fps. > >> > >> I've tried everything within avidemux, and it just doesn't seem to even > >> play > >> the Hauppauge streams with a correct audio:video sync, although changing to > >> 29-30 fps really helps. > >> > >> Just want to shrink some large TV broadcasted MPEG2 streams. Cutting > >> commercials seems to reduce the file from 8GB to 4GB. I'm seriously just > >> thinking of burning them to a Blu-Ray disk, but that's quite expensive. > >> (Thinking the later might be more feasible at this point.) > > > On Mon, Dec 24, 2012 at 09:19:25PM +0100, Emmanuel Touzery wrote: > >Are you using avidemux 2.6? > >For av in 2.5 and 2.6 work equally well for me but for tv enission > >recording (dvb-t in europe), only 2.6 works well for audio sync. > > I'm in the US using (DVB) ATSC. > > The same video, plays just fine with mplayer. Never had a problem with > audio/video sync. I used to capture video using mencoder, but then ran into > audio/video sync issues and resorted to dd. > > I'm using avidemux-2.5.6, while avidemux-2.6* series is hard masked here on > gentoo. > > I have tried playing around with exporting with different settings with no > success. > > I've also just tried cinelerra-20120707, and the audio is drifting far off > too > on playback. > > > This is TV Broadcasted video grabbed from an hvr-1950 using dd from the > /dev/dvb device. Not using mplayer/mencoder for recording as it further > processes the video before saving. > > I was using cat prior to using dd, but cat had issues with large files or > reception quality (unusual chars) or something. dd has proven more reliable. > > So, I'm using the raw original stream. > > Some things from past notes, it's been stated extra frames could be being > broadcasted to ensure quality, hence the reason for 59.940 fps when playing > with mplayer. Mplayer also starts complaining every few frames about > switching > framerate/fps. I'm I'm thinking the later might more likely be the reason. > > ---Begin of Mplayer Snip--- > demux_mpg: 24000/1001fps progressive NTSC content detected, switching > framerate. > A:34534.1 V:34535.7 A-V: -1.629 ct: -0.050 51/ 33 19% 26% 0.3% 3 0 > > demux_mpg: 30000/1001fps NTSC content detected, switching framerate. > A:34534.1 V:34535.7 A-V: -1.621 ct: -0.052 52/ 34 18% 27% 0.2% 3 0 > Warning! FPS changed 47.952 -> 59.940 (-11.988010) [7] > A:34535.2 V:34536.8 A-V: -1.641 ct: -0.113 114/ 70 11% 16% 0.2% 3 0 > > demux_mpg: 24000/1001fps progressive NTSC content detected, switching > framerate. > A:34535.4 V:34537.0 A-V: -1.586 ct: -0.133 124/ 80 10% 15% 0.2% 3 0 > > demux_mpg: 30000/1001fps NTSC content detected, switching framerate. > A:34535.4 V:34537.0 A-V: -1.598 ct: -0.135 125/ 81 10% 15% 0.2% 3 0 > Warning! FPS changed 47.952 -> 59.940 (-11.988010) [7] > A:34538.4 V:34539.9 A-V: -1.503 ct: -0.256 300/153 9% 8% 0.2% 3 0 > ---End of Mplayer Snip--- > > > The Hauppauge audio/video sync was such a popular problem on the message > boards > without any resolution, and the only thing that comes to my mind is it may > have > been fixed with a firmware update, or a unique work-araound applied quietly > within mplayer. > > Well, one things certain, I'm sure I'm on the right mailing list -- as if > anybody knows, it would be people here! And, as I said, not going to pull my > hair out on this. I usually just watch things once and discard the recorded > show anyways. Likely the issue is only with TV broadcasted material and not > with composite input recording. > > -- > Roger > http://rogerx.freeshell.org/ > _______________________________________________ > pvrusb2 mailing list > [email protected] > http://www.isely.net/cgi-bin/mailman/listinfo/pvrusb2 > -- Mike Isely isely @ isely (dot) net PGP: 03 54 43 4D 75 E5 CC 92 71 16 01 E2 B5 F5 C1 E8 _______________________________________________ pvrusb2 mailing list [email protected] http://www.isely.net/cgi-bin/mailman/listinfo/pvrusb2
