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Use Libation settings to decide which DRM is downloaded.

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This commit is contained in:
Michael Bucari-Tovo 2025-05-09 13:13:34 -06:00
parent 203ab00865
commit 19db226f5a
1 changed files with 25 additions and 73 deletions
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98
Source/FileLiberator/DownloadOptions.Factory.cs
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@ -48,8 +48,6 @@ public partial class DownloadOptions
if (!config.UseWidevine || await Cdm.GetCdmAsync() is not Cdm cdm)
return await api.GetDownloadLicenseAsync(libraryBook.Book.AudibleProductId, dlQuality);
ContentLicense? contentLic = null, fallback = null;
try
{
//try to request a widevine content license using the user's spatial audio settings
@ -60,7 +58,7 @@ public partial class DownloadOptions
_ => throw new NotSupportedException($"Unknown value for {nameof(config.SpatialAudioCodec)}")
};
contentLic
var contentLic
= await api.GetDownloadLicenseAsync(
libraryBook.Book.AudibleProductId,
dlQuality,
@ -68,81 +66,35 @@ public partial class DownloadOptions
DrmType.Widevine,
config.RequestSpatial,
codecChoice);
using var client = new HttpClient();
using var mpdResponse = await client.GetAsync(contentLic.LicenseResponse);
var dash = new MpegDash(mpdResponse.Content.ReadAsStream());
if (!dash.TryGetUri(new Uri(contentLic.LicenseResponse), out var contentUri))
throw new InvalidDataException("Failed to get mpeg-dash content download url.");
contentLic.ContentMetadata.ContentUrl = new() { OfflineUrl = contentUri.ToString() };
using var session = cdm.OpenSession();
var challenge = session.GetLicenseChallenge(dash);
var licenseMessage = await api.WidevineDrmLicense(libraryBook.Book.AudibleProductId, challenge);
var keys = session.ParseLicense(licenseMessage);
contentLic.Voucher = new VoucherDtoV10()
{
Key = Convert.ToHexStringLower(keys[0].Kid.ToByteArray()),
Iv = Convert.ToHexStringLower(keys[0].Key)
};
return contentLic;
}
catch (Exception ex)
{
Serilog.Log.Logger.Error(ex, "Failed to request a Widevine license.");
//We failed to get a widevine license, so fall back to AAX(C)
return await api.GetDownloadLicenseAsync(libraryBook.Book.AudibleProductId, dlQuality);
//We failed to get a widevine content license. Depending on the
//failure reason, users can potentially still download this audiobook
//by disabling the "Use Widevine DRM" feature.
throw;
}
if (!contentLic.ContentMetadata.ContentReference.IsSpatial && contentLic.DrmType != DrmType.Adrm)
{
/*
We got a widevine license and we have a Cdm, but we still need to decide if we WANT the file
being delivered with widevine. This file is not "spatial", so it may be no better than the
audio in the Adrm files. All else being equal, we prefer Adrm files because they have more
build-in metadata and always AAC-LC, which is a codec playable by pretty much every device
in existence.
Unfortunately, there appears to be no way to determine which codec/quality combination we'll
get until we make the request and see what content gets delivered. For some books,
Widevine/High delivers 44.1 kHz / 128 kbps audio and Adrm/High delivers 22.05 kHz / 64 kbps.
In those cases, the Widevine content size is much larger. Other books will deliver the same
sample rate / bitrate for both Widevine and Adrm, the only difference being codec. Widevine
is usually xHE-AAC, but is sometimes AAC-LC. Adrm is always AAC-LC.
To decide which file we want, use this simple rule: if files are different codecs and
Widevine is significantly larger, use Widevine. Otherwise use ADRM.
*/
fallback = await api.GetDownloadLicenseAsync(libraryBook.Book.AudibleProductId, dlQuality);
var wvCr = contentLic.ContentMetadata.ContentReference;
var adrmCr = fallback.ContentMetadata.ContentReference;
if (wvCr.Codec == adrmCr.Codec ||
adrmCr.ContentSizeInBytes > wvCr.ContentSizeInBytes ||
RelativePercentDifference(adrmCr.ContentSizeInBytes, wvCr.ContentSizeInBytes) < 0.05)
{
contentLic = fallback;
}
}
if (contentLic.DrmType == DrmType.Widevine)
{
try
{
using var client = new HttpClient();
using var mpdResponse = await client.GetAsync(contentLic.LicenseResponse);
var dash = new MpegDash(mpdResponse.Content.ReadAsStream());
if (!dash.TryGetUri(new Uri(contentLic.LicenseResponse), out var contentUri))
throw new InvalidDataException("Failed to get mpeg-dash content download url.");
contentLic.ContentMetadata.ContentUrl = new() { OfflineUrl = contentUri.ToString() };
using var session = cdm.OpenSession();
var challenge = session.GetLicenseChallenge(dash);
var licenseMessage = await api.WidevineDrmLicense(libraryBook.Book.AudibleProductId, challenge);
var keys = session.ParseLicense(licenseMessage);
contentLic.Voucher = new VoucherDtoV10()
{
Key = Convert.ToHexStringLower(keys[0].Kid.ToByteArray()),
Iv = Convert.ToHexStringLower(keys[0].Key)
};
}
catch
{
if (fallback != null)
return fallback;
//We won't have a fallback if the requested license is for a spatial audio file.
//Throw so that the user is aware that spatial audio exists and that they were not able to download it.
throw;
}
}
return contentLic;
}