questions about mpegtsdemux and ffdemux_mpegts

[Andrey Boyko]

Hi, all.


I'm looking for good MPEG transport stream demuxer and made some tests with mpegtsdemux and at first glance it looks appropriate but is under gst-plugun-bad so I tried ffdemux_mpegts also. File that I play contains 3 programs - 2 (0x21 PID video, 0x24 PID AC3 audio), 3 (0x31 PID video, 0x34 PID AC3 audio), 4 (0x41 PID video, no audio); all programs about 4.5 sec long. That what I got:

gst-launch -v filesrc location=football.ts ! mpegtsdemux program-number=3 ! mpeg2dec ! xvimagesink - fine

gst-launch -v filesrc location=football.ts ! ffdemux_mpegts .video_01 ! mpeg2dec ! xvimagesink - I see first frame, then pipeline is frozen for more than 70 sec, then is playing normally so overall time is 81 sec. video_01 here is actually the same as program-number=3 above.

But gst-launch -v filesrc location=football.ts ! ffdemux_mpegts .video_02 ! mpeg2dec ! xvimagesink - is fine; this channel has no audio. So tried to test audio output, also added queues:

gst-launch -v filesrc location=football.ts ! ffdemux_mpegts .video_01 ! queue ! mpeg2dec ! xvimagesink
gst-launch -v filesrc location=football.ts ! ffdemux_mpegts name=d d.video_01 ! queue ! mpeg2dec ! xvimagesink d.audio_01 ! queue ! a52dec ! audioconvert ! audioresample ! fakesink
gst-launch -v filesrc location=football.ts ! ffdemux_mpegts name=d d.video_01 ! queue ! mpeg2dec ! xvimagesink d.audio_01 ! queue ! a52dec ! audioconvert ! audioresample ! alsasink - all are delayed first then played normally, total time 81 sec.

At the same time

gst-launch -v filesrc location=football.ts ! mpegtsdemux program_number=3 name=d d. ! queue ! mpeg2dec ! xvimagesink d. ! queue ! a52dec ! audioconvert ! audioresample ! fakesink - fine

gst-launch -v filesrc location=football.ts ! mpegtsdemux program_number=3 name=d d. ! queue ! mpeg2dec ! xvimagesink d. ! queue ! a52dec ! audioconvert ! audioresample ! alsasink - starts playing immediately but very slowly and then more and more slower; total time 169 sec.

Any ideas what's going on?

Also, what are quality of ffmpeg plugin elements? I'm particularly interesting in ffdec_ac3, ffdec_aac, ffdec_mpeg2video, ffdec_h264, ffdec_vc1.

Thanks in advance.
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[michael smith-6-3]

On Wed, Apr 15, 2009 at 3:04 AM, Andrey Boyko <[hidden email]> wrote:
> Hi, all.
>
>
> I'm looking for good MPEG transport stream demuxer and made some tests with
> mpegtsdemux and at first glance it looks appropriate but is under
> gst-plugun-bad so I tried ffdemux_mpegts also. File that I play contains 3
> programs - 2 (0x21 PID video, 0x24 PID AC3 audio), 3 (0x31 PID video, 0x34
> PID AC3 audio), 4 (0x41 PID video, no audio); all programs about 4.5 sec
> long. That what I got:

As a general rule-of-thumb, the ffmpeg elements are of lower quality
than the gst-plugins-bad elements. That's certainly the case for the
ts demuxer. Just use mpegtsdemux.

> Also, what are quality of ffmpeg plugin elements? I'm particularly
> interesting in ffdec_ac3, ffdec_aac, ffdec_mpeg2video, ffdec_h264,
> ffdec_vc1.

The AAC decoder, at least, doesn't work very well. I wouldn't expect
the AC3 decoder to handle surround formats entirely correctly either.
The others are probably fairly good.

Mike

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[Edward Hervey]

On Wed, 2009-04-15 at 09:19 -0700, Michael Smith wrote:

> On Wed, Apr 15, 2009 at 3:04 AM, Andrey Boyko <[hidden email]> wrote:
> > Hi, all.
> >
> >
> > I'm looking for good MPEG transport stream demuxer and made some tests with
> > mpegtsdemux and at first glance it looks appropriate but is under
> > gst-plugun-bad so I tried ffdemux_mpegts also. File that I play contains 3
> > programs - 2 (0x21 PID video, 0x24 PID AC3 audio), 3 (0x31 PID video, 0x34
> > PID AC3 audio), 4 (0x41 PID video, no audio); all programs about 4.5 sec
> > long. That what I got:
>
> As a general rule-of-thumb, the ffmpeg elements are of lower quality
> than the gst-plugins-bad elements. That's certainly the case for the
> ts demuxer. Just use mpegtsdemux.

 Actually... our mpegtsdemux is so bad that for quite a big number of
use cases ffdemux_mpegts works better. But I hear fixes are on the way
(/me looks at mpegtsdemux maintainers).

>
> > Also, what are quality of ffmpeg plugin elements? I'm particularly
> > interesting in ffdec_ac3, ffdec_aac, ffdec_mpeg2video, ffdec_h264,
> > ffdec_vc1.
>
> The AAC decoder, at least, doesn't work very well. I wouldn't expect
> the AC3 decoder to handle surround formats entirely correctly either.
> The others are probably fairly good.
>
> Mike
>
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