[Libav-user] Preview video and start recording with exact same stream settings

[Audric Ackermann]

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?

Le mer. 1 janv. 2020 à 20:49, Strahinja Radman <dr.strashni at gmail.com> a
écrit :

> 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
> 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
> it reaches the key frame. Deep packet copy can be achieved with the
> following code:
>
> AVPacket packet;
> av_init_packet(&packet);
> av_packet_ref(packet, src);
> av_packet_make_writable(&packet);
>
> You can based on the decoded frames, mark a key frame packet and start
> saving from there.
>
> On Wed, Jan 1, 2020 at 10:06 AM Audric Ackermann <
> audric.ackermann at gmail.com> wrote:
>
>> Ok thank you.
>> 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?
>>
>> Like doing this, but with all important params in one step:
>>
>> Thanks
>>
>> outst->codec->width = this->codec_ctx->width;
>> outst->codec->height = this->codec_ctx->height;
>> outst->codec->pix_fmt = this->codec_ctx->pix_fmt;
>> outst->codec->time_base = this->codec_ctx->time_base;
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>
>
>
> --
>
> Regards
> Strahinja Radman
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