On Tue, 5 May 2020, Tao Zhang wrote:
Marton Balint <c...@passwd.hu> 于2020年5月5日周二 上午3:48写道：
On Sat, 2 May 2020, Tao Zhang wrote:
> Marton Balint <c...@passwd.hu> 于2020年5月2日周六 下午7:05写道：
[...]
>> I see. But you could add an option to the fifo muxer to only write header
>> when the first packet arrives. This way you will be able to use a
>> bitstream filter to buffer packets and the fifo muxer will only write
>> header when the first packet passes through the bitstream filter. Does
>> this seem OK?
> It seems OK. If nobody object it, I'm glad to add
> write_header_on_first_packet option on fifo muxer and create a new
> bitstream filter which buffers fixed duration packets.
Great. I suggest a shorter name for the option of the fifo muxer,
delay_write_header I think is enough, you can explain the details in the
docs.
Great suggestion. I'll follow it.
Also it should be pretty straightforward to add this feature to fifo.c,
from a quick look at the code one approach is to add a NOOP message type,
and if the option is set, then use that message type for the first
message, if it is not set, use the WRITE_HEADER message type, as it is
used now.
Also we should find a good name for the bitstream filter, maybe "buffer",
or "fifo", or if you want to better refer to the use case, then
"timeshift" can also work.
Maybe "caching" or "cache"?
Another thing you should think about is what should happen at the end of
the stream, when flushing the bitstream filter:
- drop pending packets
- flush pending packets as fast as possible
- flush pendning packets realtime
Maybe it should be selectable between the 3 options? I can imagine use
cases for all three possibilities.
Although I have not imagined the first and second use cases, I'm glad
to implement all three.
I have given the bitstream filter approach some additional thought and
since each stream will have a different bitstream filter I think you will
have problems when flushing them in ffmpeg.c because it will flush them
sequentially, the packet interleaving will be something like
- all remaining packets from the first stream
- all remaining packets from the second stream
... etc.
Which will cause issues at muxing the last part of the stream if the
buffer duration is larger than a few seconds.
Sorry, it looks like hacking the whole thing into fifo.c works the best
after all. The only problem is that I don't see a clean way of doing that
if you only want to enforce realtiem output there when flushing the
buffered packets...
Regards,
Marton
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