On 9/19/2021 12:28 AM, Soft Works wrote:
-----Original Message-----
From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of James Almer
Sent: Sunday, 19 September 2021 05:05
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH v2 2/2] ffprobe: Fix incorrect display of
closed_captions property
On 9/18/2021 7:10 PM, Soft Works wrote:
Repro Example:
ffprobe -show_entries stream=closed_captions:disposition=:side_data=
"http://streams.videolan.org/streams/ts/CC/NewsStream-608-ac3.ts";
While the codec string includes "Closed Captions",
the stream data is showing: closed_captions=0
The test ref was incorrect as the test media file
actually does have cc.
Signed-off-by: softworkz <softwo...@hotmail.com>
---
v2: Fix test result. It was undiscovered locally as make fate
does not seem to properly rebuild ffprobe.
fftools/ffprobe.c | 5 +++--
tests/ref/fate/ts-demux | 2 +-
2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/fftools/ffprobe.c b/fftools/ffprobe.c
index 880f05a6c2..9425c1a2e3 100644
--- a/fftools/ffprobe.c
+++ b/fftools/ffprobe.c
@@ -2678,10 +2678,11 @@ static int show_stream(WriterContext *w,
AVFormatContext *fmt_ctx, int stream_id
print_int("width", par->width);
print_int("height", par->height);
if (dec_ctx) {
+ unsigned codec_properties =
av_stream_get_codec_properties(ist->st);
Library users are meant to use their own decoder contexts if they want
this kind of information. AVStream->internal->avctx is internal to lavf.
Accessors like this should be avoided.
If you look further up in util
ffprobe is already decoding frames for the purpose of show_frames, and
in fact if you add -show_frames to the above command line example you
gave, the output of show_streams will report closed_captions=1.
Yes, I know that, but if you don't - the output is wrong.
Yeah, and fixing that would be ideal. The output of show_streams should
(if possible) not depend on other options also being passed.
Your patch will only do it for properties, and it requires new public
API, whereas my suggestion will do it for all other fields, like
coded_{width,height}, and requires changes contained entirely within
ffprobe with proper usage of existing API.
So the correct approach here is to make ffprobe decode a few frames when
you request show_streams, even if you don't request show_frames.
This is something that I would want to avoid. It has already happened
and the result is available already. The "Closed Captions" part in
the video codec string is coming from that result.
It doesn't make sense IMO, to perform another decoding run to replicate
that result, because:
- It can't be taken for granted that this will lead to the same result
that already exists
How many frames do you think would be the right amount to process?
What if the file start with a bunch of audio frames?
You decode until you get the info you need, which is what
avformat_find_stream_info() does to fill its own internal
AVCodecContext. The simplest way would be to ensure one frame per stream
is decoded.
I'm not going to approve more accessors to specific fields in
AVStream->internal->avctx (Ideally, we'd remove the few that
unfortunately already exist) because they will just not stop being added
after that. There will always be another avctx field someone wants to
use, and eventually, we'll just end up with AVStream->codec all over again.
- It takes additional processing time, which could have a huge impact
depending on how the input is being processed or a rather small
impact.
But even when the impact would be small - it could matter a lot
when you are probing a library of like 10k or 100k files.
Kind regards,
softworkz
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
