Moin Ulf, On Tue, Jan 29, 2019 at 20:50:25 +0100, Ulf Zibis wrote:
> My understanding is, that a VHS cassette player always provides a fully > interlaced analogue stream (50 half-frames per sec. for PAL). Originally coming from the analog world, I can confirm that this is true. > With this a DVD recorder has two options, (1) a interlaced vob stream > or (2) a deinterlaced progressive vob stream. Why should it create a > mixed stream? I agree. > My explanation is, that the original VHS was marked with copy > protection, so the DVD recorder by legal reasons has to sustain the > copy protection by creating an intentionally corrupted DVD file > system (which is not readable from a computer) and additionally a > corrupted vob stream, which is detected and forbidden to copy by > legal DVD copy software. This seems far fetched ("weit hergeholt"), at least in terms of creating mixed progressive/interlaced content. Broken file systems and streams: Yes, often. > It seems to me, a 25 fps interlaced stream has 25 frames per sec., each > with 2 fields, top and bottom (50 fields per sec. in total) and a 25 fps > progressive stream has 25 frames per sec., each with 1 field. > So my video with "TFF: 36759 BFF: 19705 Progressive: 58193 > Undetermined: 27" has 36759*2+19705*2+58193+27 = 171148 fields in > total, partly half, partly full ones. But idet says: "Repeated Fields: > Neither:114683 Top: 1 Bottom: 0" > > Can you please help me to understand this? (I hate the concept of interlaced digital video, BTW.) AFAIU, idet does an *interpretation* of the input, somewhat like the visual inspection. In certain cases, it will see no obvious signs of interlacing, and count the frames as progressive. So, in summary, you have a statistical analysis. Unless your DVD recorder is really doing funky magic, your recording should be interlaced. > >> Also I do not understand, that after the transcoding to mp4 the numbers > >> are different. I interpret this, that the transcoding process does some > >> deinterlacing, but you say, the encoder does not. The vob with 114684 > >> frames at 25 fps results in 1:16:27.36 length, but the resulting mp4 with > >> 114502 frames is 1:16:20.08. BTW, this difference is marginal, and probably due to the lossy nature of re-encoding biasing idet's results. > I need concentration on the subject and additionally time to > translate my thoughts from german to english. For a few of us, you could reiterate in German. That will not help the community at all, though. > What is vfr and cfr? Variable vs. constant frame rate. (Smart phone cameras *tend* to record VFR, as do some webcams which adapt frame rates to lighting conditions. Other examples exist.) Cheers and Gruß, Moritz _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".