[FFmpeg-user] A query on mpegts and global headers

Dennis Mungai dmngaie at gmail.com
Sun Aug 30 22:33:48 EEST 2020

On Sun, 30 Aug 2020 at 18:11, Gyan Doshi <ffmpeg at gyani.pro> wrote:

> On 30-08-2020 06:52 pm, Dennis Mungai wrote:
> > Hello there,
> >
> > With mpegts output, should global headers be used or not, set via -fflags
> > +global_header?
> No.
> > And if there are exceptions to that, based on the codec type wrapped in
> > mpegts, when should global headers be used for mpegts?
> Global header is for formats that store codec parameters out of band
> i.e. in container metadata. Enabling the flag tells the encoder to store
> parameters in AVStream->extradata from where it is used by muxers of
> such formats. Additionally, the flag also suppresses periodic
> announcement of these parameters within the stream (in-band).
> MPEG-TS has no global header since it is meant for use as a 'continuous'
> transport stream. to which clients may start listening at an arbitrary
> point. So periodic parameter set transmission is required.
> When generating an output for use by a single muxer, the muxer has a
> flag which will be conveyed to the encoder automatically, so the user
> doesn't have to set anything. However in case of the tee muxer, which
> sends data to multiple muxers, some of which require global headers, the
> flag has to be manually set and periodic parameter sets reinserted using
> dump_extra for muxers such as mpegts.
> Regards,
> Gyan
Many thanks for clearing that up, Gyan. Most appreciated.

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