From: Nicolas Gaullier <nicolas.gaullier@cji.paris>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH 3/6] avformat/s337m: New ff_s337m_probe()
Date: Tue, 21 Feb 2023 10:57:12 +0000
Message-ID: <MR1P264MB2483254B8091E2E0FC54A6C59BA59@MR1P264MB2483.FRAP264.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <ab454c4ccfa7f6816ddbbd9e61c03418803e84c7.camel@haerdin.se>
>> ff_s337m_probe is very similar to s337m_probe: what mainly differs is
>> the input parameters.
>> The one little thing I added is the S337M_PROBE_GUARDBAND_MIN_BYTES.
>> Currently it is set to 0, so has no effect (and of course I can remove
>> it if someone object).
>> There is two things to know about it:
>> - one is that some DolbyE decoder implementations does not support the
>> s337m sync word to be the first word, A minimal guard band (full of
>> zero) is required in such a case : 1 word is enough in the cases I
>> experimented.
>> One developer might find it useful to set
>> S337M_PROBE_GUARDBAND_MIN_BYTES to 1 in order to ffprobe-qc/reject
>> such files.
>> - one other thing is that, currently, the detection is based on 3
>> consecutive samples, But there are other implementations in the wild.
>> A common single- sample implementation is to simply require a
>> sufficient S337M_PROBE_GUARDBAND_MIN_BYTES in order to avoid a fake
>> detection.
>> (for 16 bits, this is really dangerous!; for 24 bits, I think it is
>> fair but would still require some little additions to be 100% sure).
>
>What a mess.. And there's no other way to reliably probe this?
>
>/Tomas
No! But the statistics are such that at some time, a fake probe is not "possible".
Anyway, we already have stream probings in current code, not only considering wav.
I think my patch is similar to the spdif probe and safe.
Nicolas
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next prev parent reply other threads:[~2023-02-21 10:57 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-13 18:09 [FFmpeg-devel] [PATCH 0/6] wavdev: s337m support Nicolas Gaullier
2023-02-13 18:09 ` [FFmpeg-devel] [PATCH 1/6] avformat/s337m: Split read_packet/get_packet Nicolas Gaullier
2023-02-16 10:36 ` Tomas Härdin
2023-02-13 18:09 ` [FFmpeg-devel] [PATCH 2/6] avformat/s337m: Consider container bit resolution Nicolas Gaullier
2023-02-16 10:36 ` Tomas Härdin
2023-02-17 9:44 ` Nicolas Gaullier
2023-02-21 9:47 ` Tomas Härdin
2023-02-21 10:43 ` Nicolas Gaullier
2023-02-22 10:07 ` Tomas Härdin
2023-02-13 18:09 ` [FFmpeg-devel] [PATCH 3/6] avformat/s337m: New ff_s337m_probe() Nicolas Gaullier
2023-02-16 10:36 ` Tomas Härdin
2023-02-17 10:12 ` Nicolas Gaullier
2023-02-21 9:41 ` Tomas Härdin
2023-02-21 10:57 ` Nicolas Gaullier [this message]
2023-02-13 18:09 ` [FFmpeg-devel] [PATCH 4/6] avformat/wavdec: s337m support Nicolas Gaullier
2023-02-16 10:36 ` Tomas Härdin
2023-02-17 10:30 ` Nicolas Gaullier
2023-02-21 9:53 ` Tomas Härdin
2023-02-21 12:30 ` Nicolas Gaullier
2023-02-22 10:10 ` Tomas Härdin
2023-02-13 18:09 ` [FFmpeg-devel] [PATCH 5/6] avformat/wavdec.c: Reindent after last commit Nicolas Gaullier
2023-02-13 18:09 ` [FFmpeg-devel] [PATCH 6/6] avformat/wavdec: Test s337m Nicolas Gaullier
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