Poster Frame

[Dave1024]

Hi,
What is the use of a poster frame. How it is different than other frames.
Thanks
Dave

[Selur]

as far as I know:
'poster frame'/'preview frame' = frame that will be shown until video is started
depending on the container you use, one can also set a picture i.e. movie poster that will be shown instead,..
-> it's not really frame typ like IDR-/I-/P-/B-frames but a marker that indicates that this is the frame to be shown before playback
(if no poster frame is specified normally the first or second I frame is taken)

[Dave1024]

Hi Selur,

Thanks to Ur Replay.

But i have few more doubts

Is poster frame, part of the video frame or it is part of the container. ?

How the decoder knows about the frame is poster and it is part of video elementary stream or container ? - Any specific start code for poster frame ?

can we use a JPEG image as poster frame ?

:thanks:
Dave

[Selur]

Is poster frame, part of the video frame or it is part of the container. ?
afaik for mp4/mkv sources it's part of the container (and as such needs to be specified on container creation and will be lost on remux), part of the video stream sounds bad since this would need splitter&decoder&seeking,..

How the decoder knows about the frame is poster and it is part of video elementary stream or container ?
probably not handled by the decoder, but the splitter,.. should be defined in container specification (probably optional to support it)

Any specific start code for poster frame ?
don't think so, since it's not part of the video stream

can we use a JPEG image as poster frame ?
for mp4/mkv: yes (mp4bpx and mkvmerge i.e. both only allow pictures which are not part of the stream to be preview/poster frames; afaik. other tools like Quicktime allow to select frame from the video stream, expost it to jpg and set this new jpg as poster frame in in the container)

Cu Selur

[Dave1024]

Thanks for your replay.

Let me ask a questions.

For audio codec like MP3 there is ID3 Tag is available. But in some situation other than id3 tag poster frame is there. How it is achieved.

One more question what is the difference between poster frame and freezing of frames ?

Thanks
Dave

[Selur]

as I understand it:
freezing of frames = during playback a frame shown and not replaced by a following frame (normally due to a problem with the decoding)
poster frame = see above ;)
-> first one is due to a problem when decoding the input, second one is a picture in the container
"id3 tag poster frame" -> not totally sure how it is done in mp3, but I would guess it's simply a relative link to an external image that should be shown by a player during playback (in mp4/mov/mkv it's just a picture in the container)