Hmmm....<br>
<br>
I know it seems unlikely that it's the recording side, but that's why
I've tried two different computers and then posted to the list to see
if anyone had any ideas.<br>
<br>
The first computer I tried playback on is the FE/BE combo and that's
where I saw the problem. It's a 1.6 GHz P4 so it isn't suprising it
can't keep up with HDTV.<br>
<br>
Then I tried playback on a 1.7 GHz Pentium M, which is supposed to have
more horse power per cycle than a P4 and has seemed quick on other
apps. Granted, this is pretty close to the 1.6 where I originally had
the problem so maybe it's still underpowered.<br>
<br>
One HTDV show I recorded before and which was set to transcode
automatically to MPEG4 plays well on both computers *if* I play it with
mplayer with the -framedrop parameter.<br>
<br>
However, several recordings since then, even when transcoded, don't seem to play back smoothly even with -framedrop.<br>
<br>
<br>
If anyone wants to try it, I could post a few seconds of the transcoded
content (PBS news) somewhere and you could tell me if plays back okay
for you.<br>
<br>
About MPEG4 playback being CPU intensive... are you sure? I thought
part of the benefit of MPEG4 was the high cost of encoding but the low
cost of decoding (ie, so you can play it on little hand held devices.)
The transcoded dimensions are MUCH smaller than the original, weighing
in at 352x240, which should help with the CPU usage a good bit. In
fact, when I playback on the 1.7 GHz Pentium M, CPU usage is only
25%-30% according to 'top', but the audio is still choppy.<br>
<br>
<br>
<br><div><span class="gmail_quote">On 9/14/05, <b class="gmail_sendername">Nick</b> <<a href="mailto:knowledgejunkie@gmail.com">knowledgejunkie@gmail.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
On 14/09/05, Michael T. Dean <<a href="mailto:mtdean@thirdcontact.com">mtdean@thirdcontact.com</a>> wrote:<br>> Brian McEntire wrote:<br>><br>> > I'm recording OTA HDTV with a PC HD-3000 card.<br>> >
<br>> > The video quality looks perfect, rarely pixelates, but the audio is<br>> > very bad: it sounds choppy, echos frequently, and has a pulsing<br>> > quality to it.<br>> ><br>> > I'm recording on a P3
1.6 with 768 MB RAM. From what I understand,<br>> > recording OTA HDTV doesn't take a lot of resources because the card is<br>> > just capturing the (already encoded) MPEG2 stream from within the ATSC<br>> > broadcast.
<br>> ><br>> > I think the problem does lay in the capture side though because even<br>> > if I transcode a captured show to xvid using nuvexport, the audio<br>> > still sounds the same on playback and I think those transcoded formats
<br>> > wouldn't tax the CPU enough to cause audio problems.<br>><br>> Actually, MPEG-4 (DivX, XviD, etc.) requires more resources to decode<br>> than MPEG-2. Basically, the higher the compression, the harder your CPU
<br>> has to work (for both compression and decompression). H.264 gives even<br>> more compression than MPEG-4, but will put the the best-on-the-market<br>> general-purpose CPU's to the test for decoding a 1920x1080 stream.
<br>><br>> So, how about fessing up--what kind of system are you using to play back<br>> the video? Have you tried playing it back in other players (i.e.<br>> MPlayer or xine)? Have you tested it on a Windows machine? It sounds
<br>> to me like a playback problem since--as you correctly observed--HDTV<br>> capture is just writing the already-encoded MPEG-2 stream to disk.<br><br>I'd second a playback or transcoding issue rather than a capturing
<br>problem. DVB here in the UK (like HDTV in the US) is 'recorded' by<br>'dumping' the broadcast streams to disk 'as they are' - so no<br>additional manipulation of the streams is carried out.<br><br>I'd check your audio config (are you using OSS or ALSA) and
<br>connections (how are you listening to the audio? SPDIF or analog<br>connection?) I'd also check the specs of your transcoding output - try<br>using 720x480 with stereo audio and see if anything improves.<br><br>Nick<br>
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