[Libav-user] Output to memory instead of file

[Richard Hussong]

On Wed, May 20, 2020 at 10:10 AM Jesper Taxbøl <jesper at taxboel.dk> wrote:

> Hi,
>
> I am using libavformat to encapsulate video and audio in a mpegts
> container.
>
> I have it working when I outputting to a file, but I need the data in
> memory for further distribution.
>
> I have been seeking for a callback or some other way to extract the bytes
> normally is written to the output file.
>
> How would I go about outputting the data to memory instead?
>

Use avio_open_dyn_buf and avio_close_dyn_buf to get libavformat to write to
a buffer and return the buffer address. The usual way to do it is:

// Create a dynamic buffer for your AVFormatContext and do some writes.
avio_open_dyn_buf(&avContext->pb);
av_write_frame(avContext, ...);
...
// Get the buffer contents and length, and do what you like with them.
uint8_t *buffer = 0;
int nbytes = avio_close_dyn_buf(&avContext->pb, &buffer);
if (nbytes > 0) {
  // whatever
}
av_free(buffer);

You need to do this little dance for each block of output data you want to
process.

- Richard


> Kind regards
>
> Jesper
>
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