mike wrote:


Maybe, but you're fixated on damage.

I narrowed it down a bit.

ffmpeg -i C:\input.wtv -map 0:3 -vcodec copy D:\output.wtv

vlc D:\output.wtv

The ffmpeg command in that example, is used to select streams
from the source WTV and copy them to the destination WTV.

The "map" command selects the streams, as identified when
you use ffplay

ffplay C:\input.wtv # Note stream numbers...
# Press control-c in Command Prompt, to quit

You will need to modify the above command (add parameters to it),
to "-map 0:2" for the audio stream, use "-acodec copy" to specify
just copying the audio stream. I didn't test that. I was actually
snipping out the video stream so I could run FFProbe on it.

And your TV station stream numbers will be different than mine.
My suspicion is, you'll see the audio streams at the lowest
stream number, and the video one is one-higher.

The above copied the single stream, at 1600 frames per second.
Basically as fast as the hard drive would go. The ffmpeg
operation preserves the WTV metadata, and does not re-compress
the stream. It's virtually unmodified, except stuff your
player will trip over, gets removed.

Then go test your FF and Reverse again. Mine is smoother here.

*******

This is some very quick feedback from FFprobe. This is
ATSC, 30 FPS progressive I would guess, and typically the
GOP is set at about half a second worth. I have some
other video here (VOB), where the GOP is 12 frames. This stuff
is 15 frames. The longest GOP value is around 600 (I tried
that for fun once while re-encoding something).

size=181380 --- I-frame?
size=21520
size=26452
size=54251
size=70900
size=70901
size=70901
size=70901 GOP=15 frame cadence
size=70901
size=70901
size=70901
size=70901
size=70900
size=70901
size=70901
size=177348 --- I-frame?
size=23804
size=25455

GSpot information tool, the frame checker in there, thinks
it is seeing more detail. The labeling FFprobe uses is a little
bit suspect. It's a very peculiar result, and maybe because
the video is talking-heads in a news broadcast. Movie video
would have some packets with smaller sizes than that (because
the frame to frame delta is quite small). Why is there a delta
of 70901 bytes between frames, on "talking heads" ?

Also, when it says a packet is 70900 bytes, I'm finding
the end of the packet has an all zeros section of substantial
size. Like the packet is being padded to maintain the
data rate. And I didn't think that sort of thing was necessary.
I doubt the presence of the zeros matters, because somewhere that
packet has a length field, and they might well be filling zeros
after the length has expired. I don't think other video I've looked
at, did it that way. There were long and short packets, and they
never had big zeroed sections in them.

Paul