[FFmpeg-devel] [PATCH 4/9] avformat/s337m: New ff_s337m_probe()

[Carl Eugen Hoyos]

Am Fr., 3. Jan. 2020 um 16:57 Uhr schrieb Nicolas Gaullier
<nicolas.gaullier at cji.paris>:
>
> Similar to ff_spdif_probe() with two additionnal parameters:
> - an AVClass for logging
> - the bit resolution of the container as it may be 16 or 24 for s337m
> ---
>  libavformat/s337m.c | 35 +++++++++++++++++++++++++++++++++++
>  libavformat/s337m.h | 19 +++++++++++++++++++
>  2 files changed, 54 insertions(+)
>
> diff --git a/libavformat/s337m.c b/libavformat/s337m.c
> index 5c8ab2649c..dc62d6ab98 100644
> --- a/libavformat/s337m.c
> +++ b/libavformat/s337m.c
> @@ -133,6 +133,41 @@ static int s337m_probe(const AVProbeData *p)
>      return 0;
>  }
>
> +int ff_s337m_probe(const uint8_t *buf, int size, enum AVCodecID *codec, void *avc, int container_word_bits)
> +{
> +    int pos = 0;
> +    int consecutive_codes = 0;
> +
> +    if ( size < S337M_MIN_OFFSET)
> +        return 0;
> +    size = FFMIN(2 * S337M_MAX_OFFSET, size);
> +
> +    do {
> +        uint64_t state;
> +        int data_type, data_size, offset;
> +        while (pos < size - 12 && !buf[pos]) {
> +            pos++;
> +        }
> +        if (pos >= size - 12 || pos < S337M_PROBE_GUARDBAND_MIN_BYTES)
> +            return 0;
> +        state = container_word_bits == 16 ? AV_RB32(buf + pos) : AV_RB48(buf + pos);
> +        if (!IS_LE_MARKER(state))
> +            return 0;
> +        data_type = container_word_bits == 16 ? AV_RL16(buf + pos + 4) : AV_RL24(buf + pos + 6);
> +        data_size = container_word_bits == 16 ? AV_RL16(buf + pos + 6) : AV_RL24(buf + pos + 9);
> +        if (s337m_get_offset_and_codec(avc, state, data_type, data_size, container_word_bits, &offset, codec))
> +            return 0;
> +        if (avc) {
> +            double s337m_phase = pos * 4. / container_word_bits / 48000;
> +            av_log(avc, AV_LOG_INFO, "s337m sample %d detected with phase = %.6fs\n", consecutive_codes, s337m_phase);
> +            if (*codec == AV_CODEC_ID_DOLBY_E && (s337m_phase < DOLBY_E_PHASE_MIN || s337m_phase > DOLBY_E_PHASE_MAX))
> +                    av_log(avc, AV_LOG_WARNING, "Dolby E phase is out of valid range (%.6fs-%.6fs)\n", DOLBY_E_PHASE_MIN, DOLBY_E_PHASE_MAX);
> +        }
> +    } while (++consecutive_codes < 2);
> +
> +    return AVPROBE_SCORE_MAX;
> +}

Probe functions must never av_log() anything.

Since you add an option in a later patch: Can you explain the
reasoning for the whole patchset better?
If DolbyE can be auto-detected (I assume so), this should be
done and no further option should be needed.

Carl Eugen