[FFmpeg-user] Transcode with the some properties

Boris ndjoreboris at gmail.com
Mon Nov 4 19:59:15 EET 2019

Hello Mortiz,

Le lun. 4 nov. 2019 à 17:23, Moritz Barsnick <barsnick at gmx.net> a écrit :

> Hi Boris,
> On Mon, Nov 04, 2019 at 10:29:10 +0100, Boris wrote:
> > Hello,
> > I want to transcode video with exactly the same properties of the input
> > video in the output video.
> > I use the transcoding.cc code. In the static int open_output_file(const
> > char *filename) function, I set  encoder parameters like this :
> This list (ffmpeg-users) is primarily for the use of the command line
> tool. For assistance with programming with the libav* libraries, please
> refer to the mailing list libav-user:
> https://ffmpeg.org/mailman/listinfo/libav-user
> Also please note that your code was wrapped in a fashion making it hard
> to read:
> You may want to avoid line breaks in your mailer, or attach a text file
> instead.

Thank you. I will take into account your comments and suggestions .

> > But when I run exiftool on output  video and on input video, some values
> > like video duration, encoder, bit rate,  are differente.
> > Can someone tells me how can I do to keep the same parameters (metada) of
> > the input video in the output video, please?
> What are you exactly trying to achieve? If you want *exactly* the same
> characteristics, you should probably just copy the stream (and the
> metadata) instead of re-encoding.

My aim is  to manipulate motion vectors (+- operation) while transcoding.
But I want that the output video has as much as possible the same
properties as the output video.

> Duration and bitrate are not metadata.

Ok :).

> The encoder (metadata) will be different, because it is a different
> encoder. ;-) You can manipulate the metadata though.

Can you tell me how can I perform that ?

> If you correctly determine the source's bitrate, you should be able to
> set it for the encoding, and depending on the encoder, you may achieve
> the exact same rate.
> But the input stream may have more characteristics, such as:
> - VBR,
> - GOP size, or even
> - placement of I-frames,
> - use of B-frames
> and so on. Which of these do you want to duplicate, which not? And why?
> If you specify your actual needs more precisely, it may be easier to
> come up with a recipe to fulfill them. On the other list, of course.
> ;-)

Thank you so much. .

> Cheers,
> Moritz


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