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Preseving Dolby Digital sound when decrypting HD recordings

Discussion in 'HD/HDR-FOX T2 Customised Firmware' started by imatoz, Jan 16, 2012.

  1. imatoz

    imatoz New Member

    I have tried decrypting several BBC HD recordings using the directions on the site then FTP them to my PC with Filezilla. Even when the original recording is in DD 5.1 I end up with stereo sound in AAC. Is there a way to keep the original DD 5.1 sound track? The decrypted recordings play back perfectly on an Xtreamer as TS files but only in stereo. Help please.
    Thanks to all the contributors who have so much improved the Humax HDR.
  2. neilleeds

    neilleeds Member

    Someone else will confirm but it seems very unlikely the decryption is removing the DD soundtrack.
  3. grahamlthompson

    grahamlthompson Well-Known Member

    There is no DD soundtrack. Freeview-HD uses aac audio. The box downmixes this to DD (2.0 or 5.1 as transmitted) to the digital audio outputs.
  4. imatoz

    imatoz New Member

    Thanks I didn't know that. So is the 5.1 info there in the AAC file after decryption and can I get 5.1 from the AAC track or convert it to DD 5.1 somehow?
  5. grahamlthompson

    grahamlthompson Well-Known Member

    As the file is a straight copy of the broadcast data I imagine the 5.1 data if present will still be there.

    You could try the ac3 encoder in Superc


    A Google search found this and a number of other suggestions.

  6. imatoz

    imatoz New Member

    Many thanks. I'll give it a try and report the results.
  7. ntm1275

    ntm1275 Member

    If you play the recording from the Humax before you copy it to another source it will play through an amp using DD 5.1 or 2.0 even though the audio is AAC

    If you pull the recording off the Humax and do nothing with it, and then copy it back to the Humax, you will not get DD, it will be in DProLogic 2 channel

    The copying off the Humax and then copying it back seem to loose some information that tells it to give you DD sound

    If I copy a recording off the Humax, I have to re-encode the sound to AC3 5.1 or 2.0 before copying it back to the Humax, and then it plays in DD
  8. oijonesey

    oijonesey Hummy.tv SEO Guru

    This is not a definite reply but just reading things as you've written them then that could be because the audio info you refer to as being lost on copy is in one of the 'sidecar' files that the Hummy creates - if you only copy the main TS file out and back are the other three files moving with it?
  9. grahamlthompson

    grahamlthompson Well-Known Member

    The sidecar files don't carry any audio or video information. One has navigation data to give the hdr fast forward etc capability, the other data like the channel name, prog info, dates and times recorded. The TS file has the video and audio multiplexed into the transport stream file. The sidecar files will mean nothing to a PC. The other file which you never need is the matching .tac file which has the chapter thumbnails.

    After editing a file you need to recreate new sidecar files before copying the file back to the HDR.
    Whether this will restore aac audio not sure.

    Google AV2HDR-T2
  10. Ezra Pound

    Ezra Pound Well-Known Member

    Or have a look at the Wiki HERE
  11. grahamlthompson

    grahamlthompson Well-Known Member

    Thanks for the memory jog. Reading the blurb again I see you do have to replace the aac audio with AC3.
  12. imatoz

    imatoz New Member

    I followed up on the advice I got here and have tried it on an HD recording of Victoria which I also sid usinf a Sat Card in a PC with the following results.
    The sat card recording has a DD audio file and a video file. The video file is .264 at 1980:1080i 50fps and is 7.33 Gb after demux with tsmuxer. The ac3 audio file is 386MB. The duration of the satellite recording is a few minutes longer than the DTT file due to padding.
    The Humax HDR file has two AAC audio files and a video file. The video file is shown in tsmuxer as 264 at 1980:1080p 50fps and is 3.9GB. When played back on the PC one audio file is 5.1 and the other is silent. The bigger audio file is 371MB. Thus the two audio files are similar sizes dut the satellite video showing 1080i is almost twice the size of the DTT showing 1080p.
    If I try to convert the audio without demuxing using Super it crashes. If I try to strip the silent audio file out using tsremux the remaining 5.1 file is converted to stereo. If I try using tsmuxer it doesn't see the audio files at all. Thus the comments saying that decrypting the HD should not affect the audio are correct. My mistake was caused by the use of tsmuxer to stip the silent audio file. I would appreciate advice on how to convert the audio file to ac3 I can't get super to work and demuxing the audio file to convert with an audio converter reduces it to stereo. Help please.