<div dir="ltr"><div>Well, you can do this. Keep last N number of packets in a buffer, where N is guaranteed to contain keyframe packet. When you encounter new keyframe packet<br></div><div>you can free the packets that are not needed anymore. When someone starts to record, you can mux from the last known key frame packet. </div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Jan 1, 2020 at 11:10 AM Audric Ackermann <<a href="mailto:audric.ackermann@gmail.com">audric.ackermann@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto">But if I want to avoid missing the first few frames which are not a key frame, I have to reencode the data, so the first frame recorded is a key frame, right?</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Le mer. 1 janv. 2020 à 20:49, Strahinja Radman <<a href="mailto:dr.strashni@gmail.com" target="_blank">dr.strashni@gmail.com</a>> a écrit :<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">If you only want to copy the input, there is no need to transcode. You can simply duplicate the input packets, one packet goes to the decoder so it can be shown, the other <div>goes to the muxer for the recorder when someone presses the record button. You can save to whatever format you want but input may not be playable from the start until</div><div>it reaches the key frame. Deep packet copy can be achieved with the following code:</div><div><br></div><div>AVPacket packet;<br></div><div> av_init_packet(&packet);<br> av_packet_ref(packet, src);<br> av_packet_make_writable(&packet);<br></div><div><br></div><div>You can based on the decoded frames, mark a key frame packet and start saving from there.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Jan 1, 2020 at 10:06 AM Audric Ackermann <<a href="mailto:audric.ackermann@gmail.com" rel="noreferrer" target="_blank">audric.ackermann@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(68,68,68)">Ok thank you.</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(68,68,68)">As I do not control the input parameters I will go for the transcode option. Is there an easy way to duplicate all required decoder parameters to the encoder?</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(68,68,68)"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(68,68,68)">Like doing this, but with all important params in one step:</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(68,68,68)"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(68,68,68)">Thanks<br></div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(68,68,68)"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(68,68,68)"><div style="color:rgb(212,212,212);background-color:rgb(30,30,30);font-weight:normal;font-size:14px;line-height:19px;white-space:pre-wrap"><div><span style="color:rgb(212,212,212)"> </span><span style="color:rgb(156,220,254)">outst</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">codec</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">width</span><span style="color:rgb(212,212,212)"> = </span><span style="color:rgb(86,156,214)">this</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">codec_ctx</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">width</span><span style="color:rgb(212,212,212)">;</span></div><div><span style="color:rgb(212,212,212)"> </span><span style="color:rgb(156,220,254)">outst</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">codec</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">height</span><span style="color:rgb(212,212,212)"> = </span><span style="color:rgb(86,156,214)">this</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">codec_ctx</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">height</span><span style="color:rgb(212,212,212)">;</span></div><div><span style="color:rgb(212,212,212)"> </span><span style="color:rgb(156,220,254)">outst</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">codec</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">pix_fmt</span><span style="color:rgb(212,212,212)"> = </span><span style="color:rgb(86,156,214)">this</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">codec_ctx</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">pix_fmt</span><span style="color:rgb(212,212,212)">;</span></div><div><span style="color:rgb(212,212,212)"> </span><span style="color:rgb(156,220,254)">outst</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">codec</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">time_base</span><span style="color:rgb(212,212,212)"> = </span><span style="color:rgb(86,156,214)">this</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">codec_ctx</span><span style="color:rgb(212,212,212)">-></span><span style="color:rgb(156,220,254)">time_base</span><span style="color:rgb(212,212,212)">;</span></div></div></div></div>
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