<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Thu, Mar 15, 2018 at 4:54 AM, Michael IV <span dir="ltr"><<a href="mailto:explomaster@gmail.com" target="_blank">explomaster@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><span class="">

<i><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">AVCodecParameters is for information that codecs need to do their work</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">but is stored in a structured way in the container format rather than</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">encoded in the bitstream. Codecs vary in what they need and what they</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">put in the bitstream, and formats vary in what they are able to encode,</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">but there is enough common ground for quite a few fields in</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">AVCodecParameters.</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">AVCodecContext is for actual encoding en decoding. It needs the</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">information from AVCodecParameters, but it also needs settings that are</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">specific to the process at hand.</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">Complaining that AVCodecParameters does not have a flags field is like</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">complaining that the TV magazine tells you how to turn the volume</span><br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">button on your TV.</span></i>

<div><i><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><br></span></i></div><div><i><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><br></span></i></div></span><div><span style="font-size:12.8px">Thanks you for this even more confusing explanation,

<span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">Nicolas ))</span></span></div><div><span style="font-size:12.8px"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">It is as clear as the FFMPEG API ;)  I guess,I am not working enough with </span></span></div><div><span style="font-size:12.8px"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">the av libs  to completely understand those subtle ideas.</span></span></div><div><span style="font-size:12.8px"><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><br></span></span></div><div><i><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><br></span></i></div></div>
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<br></blockquote></div><br></div><div class="gmail_extra">Hello.  I tried posting a very long version of questions along these lines but it never made it to this list.  This thread is so similar it's been revealing and I hopped on IRC to get a few answers confirmed.  Here is my understanding, please feel free to correct me if I am wrong:<br><br></div><div class="gmail_extra">AVCodecContext is everything a codec needs to encode video (including settings specific to the codec you're using).<br></div><div class="gmail_extra">AVCodecParameters is more like the "header info" (like a bitmap header) shared for all codecs.  Muxers and Demuxers will pretty much store this header info somewhere.<br><br></div><div class="gmail_extra">The AVStream::codec deprecated threw me for a long time.  But here is my new understanding (confirmed on IRC):<br><br></div><div class="gmail_extra">For encoding:<br><br><span><span>1.  Use </span>avcodec_find_encoder_by_name result is AVCodec.<br>2.  Pass that AVCodec to avformat_new_stream<span></span>.  The newly created AVStream will take the information from AVCodec and store it in its AVCodecParameters (AVStream::codecpar).<span><br></span></span></div><div class="gmail_extra"><span><span>3.  </span>Create your own AVCodecContext.<br>4.  Copy the parameters out 
of AVStream::codecpar into your own AVCodecContext using 
<span style="white-space:pre-wrap"></span>avcodec_parameters_to_context.<br></span></div><div class="gmail_extra"><span>5.  Configure your own AVCodecContext (in my case, using AVOptions).<br></span></div><div class="gmail_extra"><span>6.  Copy the newly configured parameters from AVCodecContext back to your AVStream::codecpar using 
avcodec_parameters_from_<wbr>context.<br></span></div><div class="gmail_extra"><span>7.  Do all of your encoding using your AVCodecContext and forget that AVStream::codec ever existed.<br><br>Given this workflow is the new blessed one, AVStream::codec must be unused.  Poking at the source it looks like internally, it checks to see if AVStream::codecpar is mismatched with AVStream::codec, and if so, it prefers AVStream::codec by copying it again into AVStream::codecpar.  However, all AVStream needs is AVStream::codecpar.<br><br></span></div><div class="gmail_extra"><span>Cheers.<br></span></div><div class="gmail_extra"><br></div></div>