<p dir="ltr">My jump goes from .5 sec to 1 frame. That means one key frame?</p>
<p dir="ltr">-- Sent from my Droid</p>
<div class="gmail_quote">On Sep 13, 2014 5:36 PM, "Mark Perkins" <<a href="mailto:perkins1724@hotmail.com">perkins1724@hotmail.com</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
<br>
> On 14 Sep 2014, at 5:29 am, "Justin Alcorn" <<a href="mailto:justin@jalcorn.net">justin@jalcorn.net</a>> wrote:<br>
><br>
>> On Sat, Sep 13, 2014 at 3:05 PM, John Finlay <<a href="mailto:finlay@moeraki.com">finlay@moeraki.com</a>> wrote:<br>
>> ffmpeg will only cut at a keyframe (AFAIK) and will skip to the closest<br>
>> keyframe following the position you specify. Therefore to use the<br>
>> mythfronteend editor to specify cutpoints you'll have to specify keyframes<br>
>> as the cutpoints around commercials. Unfortunately, the keyframes may not<br>
>> line up with the start and end of commercials - this is what I experience<br>
>> with ATSC MPEG2 streams.<br>
>><br>
>> An additional problem with the mythfrontend editor is that it uses 1-based<br>
>> counting of frames and ffmpeg uses 0-based so if you take the mythfrontend<br>
>> cutlist of keyframes and use it in ffmpeg you will find that ffmpeg will cut<br>
>> at the following keyframe the one specified. The workaround is to subtract 1<br>
>> from every cutlist frame number.<br>
>><br>
>> I hacked together a python script as a lossless transcoding Job to use<br>
>> ffmpeg (mythffmpeg) to cut out commercials using the mythfrontend cutlist.<br>
>> It works for MPEG2 but I don't know about H264 but in theory it should work.<br>
>> Look at the ffmpeg segment muxer<br>
>> (<a href="https://www.ffmpeg.org/ffmpeg-formats.html#segment_002c-stream_005fsegment_002c-ssegment" target="_blank">https://www.ffmpeg.org/ffmpeg-formats.html#segment_002c-stream_005fsegment_002c-ssegment</a>)<br>
>> for documentation.<br>
><br>
> OK, that info helps. One problem is that the script I found<br>
> translates the Myth cutlist to seconds and uses that to specify the<br>
> cuts. I guess I better switch to using frames. I assume there's some<br>
> way to do that in ffmpeg?<br>
><br>
> The biggest unanswered question - HOW do I always specify keyframes as<br>
> cutpoints? I don't know how to find keyframes.<br>
><br>
<br>
When using the cutlist editor you can use up/down arrows to change the jump by amount. When I get to where I want the cut I just change to jump by keyframes then move left / right to pick the keyframe I want or suits the best.<br>
<br>
> Sorry, but I'm still pretty new at video.<br>
><br>
> --<br>
> Justin B. Alcorn<br>
> PGP Fingerprint A36D D691 C5B0 BE15 5A2A AF49 AA1C 372C<br>
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</blockquote></div>