[FFmpeg-devel] webm streaming

[jianwen chen]

On Sat, May 14, 2011 at 11:43 PM, jianwen chen <jianwen.chen.video at gmail.com
> wrote:

> On Fri, May 13, 2011 at 12:01 AM, Dirk Griffioen <dirk at code-shop.com>wrote:
>
>>
>> >
>> > Great, on the website, it mentions "A live Matroska stream is different
>> than
>> > a file, because it may have no known end (only when the client
>> disconnects).
>> > For that the Segment *must* use the "unknow" size (all 1s in the size).
>> The
>> > other option would be to concatenate Segments with known sizes one after
>> the
>> > other. This solution allows a change of codec/resolution between each
>> > segment which can be useful in some cases (switch between 4:3 and 16:9
>> in
>> > some TV programs for example).  "
>> >
>> > I have test concatenate segments with know size together, but it dose
>> not
>> > work. Maybe the approach I try to concatenate the segments is not
>> correct.
>> > Is there anybody can help?
>> >
>>
>> I dont have time at the moment, but I would suggest to look at the
>> gstreamer patch
>>
>> there is also: http://realmike.org/
>>
>> which describes how to do it with a little python help (see the
>> matroska_live_filter.py script), this also might give valueable clue
>>
>
>
>  Thanks, Dirk,  I will read it. I hope I could figure it out and then I can
> contribute to this requirement in FFmpge.
>

I have read the code and the webpages, according to the code and the
Matroska specification, we know a live stream is designated by setting the
“Segment” size to “unknown”.  I set the size to a very large value and
setting the duration of the video to 100 hours as the python script does.
And I also delete the “SeekHead” elements ) and “Cues” elements in 2 mkv
files.

cat  1split-004-largesize-
changeduration-removeseekhead-recues.webm
2split-001-large-chaduration-rmseek-rmcue.webm > aaa.webm

But the file aaa.webm can only be played for the 1st segment.

What I want to do is concatenate the 2 segments together as a file and the
file can be played one segment by one segment.
Is there anything wrong above result in this?

The detailed info is followed:
File1
# mkvinfo 1split-004-largesize-changeduration-removeseekhead-recues.webm
+ EBML head
|+ EBML version: 1
|+ EBML read version: 1
|+ EBML maximum ID length: 4
|+ EBML maximum size length: 8
|+ Doc type: webm
|+ Doc type version: 2
|+ Doc type read version: 2
+ Segment, size unknown
|+ EbmlVoid (size: 4045)
|+ Segment information
| + Timecode scale: 1000000
| + Muxing application: libebml v1.0.0 + libmatroska v1.0.0
| + Writing application: mkvmerge v4.0.0 ('The Stars were mine') built on
Jun 17 2010 18:47:20
| + Duration: 2766143.488s (768:22:23.488)
| + Date: Wed May 11 06:02:42 2011 UTC
| + Segment UID: 0xfb 0x46 0x6a 0x88 0x4f 0xab 0xd3 0x94 0xa1 0xfd 0xf6 0xa7
0xba 0x5d 0x60 0x35
|+ Segment tracks
| + A track
|  + Track number: 1
|  + Track UID: 1
|  + Track type: video
|  + Default flag: 0
|  + MinCache: 1
|  + Codec ID: V_VP8
|  + Default duration: 41.708ms (23.976 fps for a video track)
|  + Language: und
|  + Video track
|   + Pixel width: 640
|   + Pixel height: 360
|   + Display width: 640
|   + Display height: 360
| + A track
|  + Track number: 2
|  + Track UID: 2
|  + Track type: audio
|  + Default flag: 0
|  + Codec ID: A_VORBIS
|  + CodecPrivate, length 4189
|  + Language: und
|  + Audio track
|   + Sampling frequency: 44100
|   + Channels: 2
|+ EbmlVoid (size: 1081)
|+ Cluster

File2
$ mkvinfo 2split-001-large-chaduration-rmseek-rmcue.webm
+ EBML head
|+ EBML version: 1
|+ EBML read version: 1
|+ EBML maximum ID length: 4
|+ EBML maximum size length: 8
|+ Doc type: webm
|+ Doc type version: 2
|+ Doc type read version: 2
+ Segment, size unknown
|+ EbmlVoid (size: 4045)
|+ Segment information
| + Timecode scale: 1000000
| + Muxing application: libebml v1.0.0 + libmatroska v1.0.0
| + Writing application: mkvmerge v4.0.0 ('The Stars were mine') built on
Jun 17 2010 18:47:20
| + Duration: 8585740.288s (2384:55:40.288)
| + Date: Wed May 11 06:09:38 2011 UTC
| + Segment UID: 0x12 0xea 0xf1 0x7f 0xb0 0x17 0x15 0x97 0xfb 0x67 0xd7 0x7b
0x91 0x28 0x2d 0xa3
|+ Segment tracks
| + A track
|  + Track number: 1
|  + Track UID: 1
|  + Track type: video
|  + Default flag: 0
|  + MinCache: 1
|  + Codec ID: V_VP8
|  + Default duration: 41.708ms (23.976 fps for a video track)
|  + Language: und
|  + Video track
|   + Pixel width: 640
|   + Pixel height: 360
|   + Display width: 640
|   + Display height: 360
| + A track
|  + Track number: 2
|  + Track UID: 2
|  + Track type: audio
|  + Default flag: 0
|  + Codec ID: A_VORBIS
|  + CodecPrivate, length 4189
|  + Language: und
|  + Audio track
|   + Sampling frequency: 44100
|   + Channels: 2
|+ EbmlVoid (size: 1081)
|+ Cluster


By the way, I find, if I just
 cat 1file 2 file > test.webm
without any modification of the original mkv files, the test webm file can
be played well by vlc, but can not played correctly by Mplayer.


Thanks,
Jianwen