Support ffmpeg png output as stream for thumbnail creation?

[tmacneil]

I was experimenting with the ffmpeg transcode engine in srs and noticed that only the libx264 vcodec was supported for output. I was trying to setup a transcode configuration to create a thumbnail every 60 seconds but the only file output I could create was flv. Do you have any plans to allow PNG output as well so that web browser compatible images could be created during the stream?

[winlinvip]

Yep, transcode should support png output.
Can u tell me the command to transcode rtmp to png by ffmpeg?

[tmacneil]

I use the following ffmpeg command to create a single frame png thumbnail
from an rtmp stream once every 10s. It creates a file for every frame:

/usr/bin/ffmpeg -i rtmp://127.0.0.1:1935/live?vhost=dev/stream -vf fps=1/6
-vcodec png -an -f image2 -y /tmp/thumb/live/stream_%06d.png

tmacneil@ubuntu-VirtualBox:/tmp/thumb/live$ ll *.png
-rw-rw-r-- 1 tmacneil tmacneil 131554 Oct 16 09:01 stream_000001.png
-rw-rw-r-- 1 tmacneil tmacneil 129136 Oct 16 09:01 stream_000002.png
-rw-rw-r-- 1 tmacneil tmacneil 124447 Oct 16 09:01 stream_000003.png

tmacneil@ubuntu-VirtualBox:/tmp/thumb/live$ file stream_000001.png
stream_000001.png: PNG image data, 320 x 240, 8-bit/color RGB,
non-interlaced

Here's the command for creating jpg thumbnails instead of png:

/usr/bin/ffmpeg -i rtmp://127.0.0.1:1935/live?vhost=dev/stream -vf fps=1/6
-vcodec mjpeg -an -f image2 -y /tmp/thumb/live/stream_%06d.jpg

tmacneil@ubuntu-VirtualBox:/tmp/thumb/live$ ll *.jpg
-rw-rw-r-- 1 tmacneil tmacneil 7866 Oct 16 09:02 stream_000001.jpg
-rw-rw-r-- 1 tmacneil tmacneil 12129 Oct 16 09:02 stream_000002.jpg
-rw-rw-r-- 1 tmacneil tmacneil 12772 Oct 16 09:02 stream_000003.jpg

tmacneil@ubuntu-VirtualBox:/tmp/thumb/live$ file stream_000001.jpg
stream_000001.jpg: JPEG image data, JFIF standard 1.02, comment:
"Lavc56.1.100"

I use the -ss and -vframes options to pull just a single frame after at a
certain point in the stream and then exit. For example:

/usr/bin/ffmpeg -i rtmp://127.0.0.1:1935/live?vhost=dev/stream -vf fps=1/6
-vcodec png -f image2 -an -y -ss 00:00:05.000 -vframes 1
/tmp/thumb/live/single_frame.png

tmacneil@ubuntu-VirtualBox:/tmp/thumb/live$ ll single*
-rw-rw-r-- 1 tmacneil tmacneil 130080 Oct 16 09:04 single_frame.png

tmacneil@ubuntu-VirtualBox:/tmp/thumb/live$ file single_frame.png
single_frame.png: PNG image data, 320 x 240, 8-bit/color RGB, non-interlaced

I haven't tested how SRS handles a graceful exit from ffmpeg. I'll test
that shortly, but if it sees the graceful exit as a good thing and doesn't
restart, you'd be able to get the single thumbnail if desired.

• MacNeil

On Thu, Oct 15, 2015 at 10:29 PM, winlin notifications@github.com wrote:

Yep, transcode should support png output.
Can u tell me the command to transcode rtmp to png by ffmpeg?

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#502 (comment)
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TRANS_BY_GPT3

[winlinvip]

I see, what about the following workflow for snapshot?

1. Encoder, for instance, FMLE or FFMPEG start to publish RTMP stream to SRS.
2. SRS start a transcoder specified by transcode of config, where the transcoder can be a bash script.
3. The bash script exec the ffmpeg to snapshot, which is the command of your single frame snapshot /usr/bin/ffmpeg -i rtmp://127.0.0.1:1935/live?vhost=dev/stream -vf fps=1/6 -vcodec png -f image2 -an -y -vframes 1 /tmp/thumb/live/single_frame.png
4. The bash script sleep a while, for instance, 10s when ffmpeg process gracefully exit.
5. The bash script wakeup and snapshot again.

The bash script can also exec ffmpeg by your multiple frame commad /usr/bin/ffmpeg -i rtmp://127.0.0.1:1935/live?vhost=dev/stream -vf fps=1/6 -vcodec png -an -f image2 -y /tmp/thumb/live/stream_%06d.png.

Is this ok for you?

[winlinvip]

SRS will start the transcoder when encoder start to publish stream, and terminate it when encoder stop to publish.
I think it's better for SRS to fork a bash script(or python, or another process) to manage the ffmpeg and restart or gracefully kill ffmpeg.
What's your advise?

[tmacneil]

That's not too different from the workaround I came up with this weekend.
I use the onPublish http callback to a golang app which kicks off a
background task that runs ffmpeg and manages the output. This actually
works out quite well for me because I can then do any image manipulation I
want with the image. I think I will stick with this approach because of
how much added functionality it gives me. Thank you!

On Sun, Oct 18, 2015 at 6:31 PM, winlin notifications@github.com wrote:

SRS will start the transcoder when encoder start to publish stream, and
terminate it when encoder stop to publish.
I think it's better for SRS to fork a bash script(or python, or another
process) to manage the ffmpeg and restart or gracefully kill ffmpeg.
What's your advise?

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#502 (comment)
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TRANS_BY_GPT3

[winlinvip]

So, for the snapshot feature, there are two ways:

1. Use http-callback, like what you do.
2. Use transcoder, which should support the workflow defined by Support ffmpeg png output as stream for thumbnail creation? #502 (comment)

Agree?

[tmacneil]

Agreed

On Sun, Oct 18, 2015, 11:03 PM winlin notifications@github.com wrote:

So, for the snapshot feature, I think SRS can:

1. Use http-callback, like what you do.
2. Use transcoder, which should support the workflow defined by Support ffmpeg png output as stream for thumbnail creation? #502
   (comment)
   Support ffmpeg png output as stream for thumbnail creation? #502 (comment)

Agree?

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#502 (comment)
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TRANS_BY_GPT3

[winlinvip]

Add to feature list of SRS3:
https://github.com/simple-rtmp-server/srs/wiki/v1_CN_Product#release30
https://github.com/simple-rtmp-server/srs/wiki/v1_EN_Product#release30

[winlinvip]

Add wiki for snapshot:
https://github.com/simple-rtmp-server/srs/wiki/v3_CN_Snapshot
https://github.com/simple-rtmp-server/srs/wiki/v3_EN_Snapshot

[winlinvip]

For the api-server which handle the snapshot, it will generate some thumbnail and choose the best one, read 1aa4502