[streaming] Re: Playing stream at twice normal speed, forward / backward?

[Damien LUCAS]

j.zorko at att.net wrote:
> I'm looking into how to make VLS do stream seeking i.e. fast-forward, rewind.

Good idea !

> In other words, does VLS not bother decoding 
> the PS stream any further past the PES packet headers, instead depending
 > on libffmpeg perhaps to do all of the lower-level stuff?

That's right, VLS only decodes the MPEG system layer and does not bother 
at all further levels.

> How would any of you recommend adding FF / REW to VLS?  Perhaps there is
 > a better way to do it, that would not demand that I hack VLS to decode
 > own to the frame level in order to determine whether to send a packet
 > to the provider?

I was thinking about changing the streaming process of VLS:

Current architecture:

READER -> CONVERTER -> STREAMER

Converters can be ps2ts ts2ts and raw2ts.
I think we should make a difference between:
- system layer converters
- low level converters

The low level converters would be:
- raw   -> mpeg1 (using ffmpeg)
- raw   -> mpeg4 (using ffmpeg)
- mpeg2 -> mpeg2
- mpeg2 -> mpeg4 (using ffmpeg)

A converter would be a system layer converter and a low level converter:

system decoder -> low-level converter -> system encoder

This would enable VLS to do live transcoding. In those converters, VLS 
would be able to decode PES, so you would have the possibility to read 
only I-frames for seeking.

Unfortunately, I don't have much time currently and did not begin 
anything like this, so I can't tell you when this new architecture would 
be ready.

Do you have any remark about this architecture ?

Regards,

-- 
nitrox

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