emby-toolbox/EmbyToolbox/Services/FfprobeAudioInfoParser.cs

using System.Globalization;
using System.Text.Json;

namespace EmbyToolbox.Services;

/// <summary>
/// Извлечение количества аудиодорожек и оценка суммарного размера аудио по JSON ffprobe.
/// </summary>
public static class FfprobeAudioInfoParser
{
    public static FfprobeAudioInfo? TryParse(string json)
    {
        if (string.IsNullOrWhiteSpace(json))
        {
            return null;
        }

        try
        {
            using var doc = JsonDocument.Parse(json);
            return ParseRoot(doc.RootElement);
        }
        catch
        {
            return null;
        }
    }

    private static FfprobeAudioInfo? ParseRoot(JsonElement root)
    {
        if (root.ValueKind != JsonValueKind.Object)
        {
            return null;
        }

        double? formatDurationSec = null;
        if (root.TryGetProperty("format", out var format) && format.ValueKind == JsonValueKind.Object)
        {
            formatDurationSec = TryReadDurationSeconds(format);
        }

        if (!root.TryGetProperty("streams", out var streams) || streams.ValueKind != JsonValueKind.Array)
        {
            return new FfprobeAudioInfo(0, null, false);
        }

        var audioList = new List<JsonElement>();
        foreach (var stream in streams.EnumerateArray())
        {
            if (stream.ValueKind == JsonValueKind.Object &&
                stream.TryGetProperty("codec_type", out var ct) &&
                ct.ValueKind == JsonValueKind.String &&
                string.Equals(ct.GetString(), "audio", StringComparison.OrdinalIgnoreCase))
            {
                audioList.Add(stream);
            }
        }

        var count = audioList.Count;
        if (count == 0)
        {
            return new FfprobeAudioInfo(0, 0, false);
        }

        var partial = false;
        var totalBytes = 0.0;
        var anySize = false;

        foreach (var stream in audioList)
        {
            var duration = TryReadStreamDurationSeconds(stream) ?? formatDurationSec;
            var bps = TryReadBitrateBps(stream);
            if (duration is null || bps is null)
            {
                partial = true;
                continue;
            }

            if (double.IsNaN(duration.Value) || double.IsInfinity(duration.Value) || duration.Value <= 0)
            {
                partial = true;
                continue;
            }

            if (bps.Value <= 0)
            {
                partial = true;
                continue;
            }

            totalBytes += duration.Value * (bps.Value / 8.0);
            anySize = true;
        }

        int? sizeMb;
        if (!anySize)
        {
            sizeMb = null;
        }
        else
        {
            var mb = totalBytes / (1024.0 * 1024.0);
            sizeMb = (int)Math.Round(mb, MidpointRounding.AwayFromZero);
        }

        return new FfprobeAudioInfo(count, sizeMb, partial);
    }

    private static double? TryReadDurationSeconds(JsonElement el)
    {
        if (el.TryGetProperty("duration", out var d) && d.ValueKind == JsonValueKind.String)
        {
            if (double.TryParse(d.GetString(), NumberStyles.Any, CultureInfo.InvariantCulture, out var s))
            {
                return s;
            }
        }

        return null;
    }

    private static double? TryReadStreamDurationSeconds(JsonElement stream)
    {
        return TryReadDurationSeconds(stream);
    }

    private static long? TryReadBitrateBps(JsonElement stream)
    {
        if (stream.TryGetProperty("bit_rate", out var br) && br.ValueKind == JsonValueKind.String)
        {
            var s = br.GetString();
            if (long.TryParse(s, NumberStyles.Any, CultureInfo.InvariantCulture, out var b) && b > 0)
            {
                return b;
            }
        }

        if (stream.TryGetProperty("max_bit_rate", out var mbr) && mbr.ValueKind == JsonValueKind.String)
        {
            var s = mbr.GetString();
            if (long.TryParse(s, NumberStyles.Any, CultureInfo.InvariantCulture, out var b) && b > 0)
            {
                return b;
            }
        }

        if (stream.TryGetProperty("tags", out var tags) && tags.ValueKind == JsonValueKind.Object)
        {
            foreach (var p in tags.EnumerateObject())
            {
                if (p.Name.Contains("BPS", StringComparison.OrdinalIgnoreCase) &&
                    p.Value.ValueKind is JsonValueKind.String or JsonValueKind.Number)
                {
                    if (p.Value.ValueKind == JsonValueKind.String && long.TryParse(p.Value.GetString(), NumberStyles.Any, CultureInfo.InvariantCulture, out var b) && b > 0)
                    {
                        return b;
                    }

                    if (p.Value.ValueKind == JsonValueKind.Number && p.Value.TryGetInt64(out var n) && n > 0)
                    {
                        return n;
                    }
                }
            }
        }

        return null;
    }
}

public readonly record struct FfprobeAudioInfo(int AudioStreamCount, int? AudioSizeMbTotal, bool IsPartial);