| From: "Paulus, Mark G" <[email protected]> | What about installing M$ Windows on that machine, or moving the card | to a M$ Windows machine, and make a recording there? Then you can run | ffmpeg against that file and see if it's the card or firmware.
Good suggestion. With some effort, I switched the card to a machine with a Vista installation, installed the card and played. The recording by Vista's recorder also had the same characteristic: ffmpeg made the same complaint. | From: Chris Kennedy <[email protected]> | I think this is because the MPEG2 is interlaced and so technically | holding 60 half frames but displayed as 30~ whole frames per second. | Actually ffmpeg will give you this error from files it has created | itself, like asf/wmv1/wmav2 do this. | | Newer versions of ffmpeg don't output the message for the MPEG2 produced | by the cx3241X chips, older ffmpeg's didn't always calculate this | correctly because of the interlaced nature of the MPEG. That too seems to be true. I built an ffmpeg from the development tree and did not get that message. Too bad that the version in Ubuntu 10.04 isn't that new. | From: Andy Walls <[email protected]> | On Thu, 2010-06-10 at 15:25 -0400, D. Hugh Redelmeier wrote: | > Googling through the ffmpeg list, it seems that this comes up once in a | > while. They don't seem to answer people's questions on this anymore. But | > this message seems to make it clear that they would consider this a | > bug in whatever created the file. | > | > <http://lists.mplayerhq.hu/pipermail/ffmpeg-user/2008-December/018095.html> | > | > The video container specifies a framerate, as does the video | > stream itself. | | That's technically incorrect. ffmpeg is measuring the frame rate in the | video stream. | | http://git.ffmpeg.org/?p=ffmpeg;a=blob;f=libavformat/avformat.h;h=57a6bcec4a8480554d2ea593ba989b0bb00bb3e7;hb=HEAD#l411 | | (Note that the comment in that code is also not consistent: the | comment's example 50/1 = 90000/1800 is not the lowest frame rate, | 90000/3600 = 25/1 is the lowest rate in the example.) Very interesting! Thanks for sussing this out. | > Is MythTV setting up the HVR-1600 incorrectly, causing this problem? | | That is unlikely. There are a however number of MPEG encoder related | controls, that you may want to tweak with v4l2-ctl to see the effects. | | I have a hard time seeing this as a serious problem. I'm assuming | playback happens properly given the presentation time stamps in every | PES header. What are the symptoms that you are experiencing aside from | an ffmpeg gripe? My real problem is my MythTV recordings are failing to play back on various devices that claim to be able to play back MPEG-2 recordings. Since they don't really say *why* they are unhappy, I'm grasping at any anomallies that I do find. This message from ffmpeg was one. You can see more about my problems here: <http://www.mythtv.org/pipermail/mythtv-users/2010-May/288527.html> <http://www.mythtv.org/pipermail/mythtv-users/2010-June/290280.html> (The second is the same thread but the "next" link doesn't cross month boundaries.) | > Is the cx18 driver wrong? | | The driver only has two things it can tell the firmware about the video | to be encoded using the CX18_CPU_SET_VIDEO_IN firmware command: 0 | meaning 29.97 frames/sec, or 1 meaning 25 frames/sec. Sounds hard to get wrong. | > Is the firmware wrong? | | If we assume that ffmpeg is reading data out of the MPEG-2 headers | properly, then the firmware is using 59.94 Hz as a "frame rate", which | technically it is not. So maybe that is wrong. However, I also have | not spent the Swiss Francs on a copy of the MPEG-2 standard. It could | be the case that semantically the frame rate field is used for both | frame rates and field rates. | | Fixing the problem likely means hacking the firmware - which I have no | plans to do - or asking Conexant to change the firmware - for which I'd | expect some throrough analysis of the output stream is required to show | the suspected non-compliance with the MPEG-2 standard. Yeah. A cheap hack would be to find what bits to zap in a particular recording and then try the result on some ot the players. Thanks! _______________________________________________ ivtv-devel mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-devel
