Re: "TS packets to determine frame type"

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> On 30 May 2016, at 22:45, Richard F <lists@xxxxxxxxxxxxxxxxxxxxx> wrote:
> 
> Hi Klaus,
> 
> I'm 99% of the way to finishing my H264 ffmpeg transcoding script, I'm just getting 2 of these warnings when reindexing transcoded files
> 
> May 30 21:08:09 ha-server vdr: [31785] WARNING: required 5 video TS packets to determine frame type
> May 30 21:08:09 ha-server vdr: [31785] WARNING: required 5 video TS packets to determine frame type
> 
> Sometimes the number is 4. Fortunately not over 6 yet.
> Is this a functional problem ? (files play in everything I need them to).
> I reduced the I-frame gap which also improves seeking performance, but that's not the issue.
> 
> Looking at the code I'm not quite sure what it's looking for - can you help?
> 
> I may be able to adjust codec / muxer to avoid warnings

Hello Richard,

VDR scans the TS packets in order to determine where a new frame starts
(unfortunately the authors of the DVB standard and codecs buried that
information deep in the data, instead of flagging it at the top TS level).
In doing so, it only checks as few TS packets as possible, and usually
it finds that information in the first few packets of a frame. The warning
message you get means that the information was found later than usual.
This may be caused by audio TS packets that are interspersed with the video
packets. Imagine a frame starting with one or two video TS packets (that don’t
yet contain the frame start info) and then being followed by several audio
TS packets. All these need to be buffered before the important video TS
packets can be seen. For performance reasons this buffering is kept minimal,
and the warning indicates the more of the buffer than usual is used.
Hope I was able to clear things up a little.

Klaus


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