From: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
To: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
Cc: "r.verdejo@samsung.com" <r.verdejo@samsung.com>,
"nicolas@ndufresne.ca" <nicolas@ndufresne.ca>,
" <skhan@linuxfoundation.org>,
"@lists.linuxfoundation.org,
linux-kernel-mentees@lists.linuxfoundation,
"linux-media@vger.kernel.org\"
<linux-media@vger.kernel.org>,
"@lists.linuxfoundation.org, skhan@linuxfoundation.org,
"org\"" <linux-kernel-mentees@lists.linuxfoundation.org>,
"linux-kernel@vger.kernel.org\"
<linux-kernel@vger.kernel.org>"@osuosl.org
Subject: Re: [Linux-kernel-mentees] [v10 0/4] media: vidtv: Implement a virtual DVB driver
Date: Fri, 11 Sep 2020 15:56:40 +0200 [thread overview]
Message-ID: <20200911155640.79a15a14@coco.lan> (raw)
In-Reply-To: <20200911151046.076abb79@coco.lan>
Em Fri, 11 Sep 2020 15:10:46 +0200
Mauro Carvalho Chehab <mchehab+huawei@kernel.org> escreveu:
> Em Fri, 11 Sep 2020 09:18:20 -0300
> "Daniel W. S. Almeida" <dwlsalmeida@gmail.com> escreveu:
> > > 3. dvbv5-zap wrote an empty audio file (without -P flag).
> > > Probably there are still some issues at the program
> > > channel descriptor or service;
> >
> > I don't remember whether I tried this. I tried dumping the stream to a
> > file with dvbzap, which should work. By the way, I guess we should be
> > comparing the output to this
> >
> > $ ffmpeg -f lavfi -i sine=frequency=1000:duration=5 -ac 2 -c:a s302m
> > -strict -2 out.ts
> >
> > Since it produces a playable transport stream file that actually sounds
> > like a sine tone.
> >
> > Inspecting ffmpeg & vidtv output side by side in dvbinspector, you'll
> > see that they're mostly the same. I have a separate PID for the PCR and
> > some other minor differences.
>
> The problem is here:
>
> $ dvbv5-zap -c dvb_channel.conf "S302m: Sine Wave PCM Audio" -t 30 -o pcm_audio.ts -P
> using demux 'dvb0.demux0'
> reading channels from file 'dvb_channel.conf'
> service has pid type 06: 273
>
> See, it identified the EL type ID as type 6, which is handled by
> dvbv5 library here:
>
> case 0x06: /* private data */
> /*
> * Those can be used by sub-titling, teletext and/or
> * DVB AC-3. So, need to seek for the AC-3 descriptors
> */
> dvb_desc_find(struct dvb_desc_service, desc, stream, AC_3_descriptor)
> has_ac3 = 1;
>
> dvb_desc_find(struct dvb_desc_service, desc, stream, enhanced_AC_3_descriptor)
> has_ac3 = 1;
>
> if (has_ac3) {
> entry->audio_pid = realloc(entry->audio_pid,
> sizeof(*entry->audio_pid) *
> (audio_len + 1));
> entry->audio_pid[audio_len] = pid;
> audio_len++;
> } else {
> entry->other_el_pid = realloc(entry->other_el_pid,
> sizeof(*entry->other_el_pid) *
> (other_len + 1));
> entry->other_el_pid[other_len].type = stream->type;
> entry->other_el_pid[other_len].pid = pid;
> other_len++;
> }
> break;
>
> Basically, it is not recognizing the stream as an audio PID, but
> as some other random data. Due to that, the output of
> dvb_channel.conf will be wrong.
>
> As type 6 seems to be the correct one for SMPTE 302M, we need to fix
> dvbv5-tools (and likely other tools like kaffeine), in order to
> recognize it as audio as well.
Ok, I guess I got what should be done here. ETSI TS 102 154 says that
SMPTE 302M should use the "registration_descriptor".
From the specs, such descriptor should be filled with
format_identifier = 0x42535344.
We need to add this on both at v4l-utils and at the vidtv driver.
Thanks,
Mauro
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next prev parent reply other threads:[~2020-09-11 13:56 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 12:58 [Linux-kernel-mentees] [v10 0/4] media: vidtv: Implement a virtual DVB driver Daniel W. S. Almeida
2020-08-21 12:58 ` [Linux-kernel-mentees] [v10 1/4] media: vidtv: implement a tuner driver Daniel W. S. Almeida
2020-08-21 12:58 ` [Linux-kernel-mentees] [v10 2/4] media: vidtv: implement a demodulator driver Daniel W. S. Almeida
2020-08-21 12:58 ` [Linux-kernel-mentees] [v10 3/4] media: vidtv: add a bridge driver Daniel W. S. Almeida
2020-09-15 11:53 ` Geert Uytterhoeven
2020-09-15 13:26 ` Daniel W. S. Almeida
2020-09-15 13:35 ` Geert Uytterhoeven
2020-09-15 18:13 ` Daniel W. S. Almeida
2020-09-16 7:01 ` Mauro Carvalho Chehab
2020-08-21 12:58 ` [Linux-kernel-mentees] [v10 4/4] media: Documentation: vidtv: Add ReST documentation for vidtv Daniel W. S. Almeida
2020-09-11 8:02 ` [Linux-kernel-mentees] [v10 0/4] media: vidtv: Implement a virtual DVB driver Mauro Carvalho Chehab
2020-09-11 12:18 ` Daniel W. S. Almeida
2020-09-11 13:10 ` Mauro Carvalho Chehab
2020-09-11 13:56 ` Mauro Carvalho Chehab [this message]
2020-09-12 2:54 ` Daniel W. S. Almeida
2020-09-12 7:38 ` Mauro Carvalho Chehab
2020-09-12 8:21 ` Hans Verkuil
2020-09-12 9:15 ` Mauro Carvalho Chehab
2020-09-12 14:49 ` Daniel W. S. Almeida
2020-09-12 17:57 ` Mauro Carvalho Chehab
2020-09-14 8:33 ` Hans Verkuil
2020-09-12 8:35 ` Hans Verkuil
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