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I have downloaded this video http://www.youtube.com/watch?v=CpznCSeqMxw as a flv file. When I now try to play it, mplayer says

Audio: no sound

and shows the video, but no sound (which is, why I have downloaded the video—to have the sound).

And VLC refuses to play it at all. No error message. I am confused.

The file type in Linux:

$ file Space\ Night\ -\ Earth\ Views\ 4-5.flv 
Space Night - Earth Views 4-5.flv: ISO Media

And some more information from mplayer:

$ mplayer -frames 0 -identify Space\ Night\ -\ Earth\ Views\ 4-5.flv 2> /dev/null | grep -i 'audio\|sound\|video\|clip'
ID_VIDEO_ID=0
[lavf] stream 0: video (h264), -vid 0
VIDEO:  [H264]  600x480  24bpp  25.000 fps  338.6 kbps (41.3 kbyte/s)
Clip info:
ID_CLIP_INFO_NAME0=major_brand
ID_CLIP_INFO_VALUE0=dash
ID_CLIP_INFO_NAME1=minor_version
ID_CLIP_INFO_VALUE1=0
ID_CLIP_INFO_NAME2=compatible_brands
ID_CLIP_INFO_VALUE2=iso6avc1mp41
ID_CLIP_INFO_NAME3=creation_time
ID_CLIP_INFO_VALUE3=2013-07-03 06:36:36
ID_CLIP_INFO_N=4
ID_VIDEO_FORMAT=H264
ID_VIDEO_BITRATE=338576
ID_VIDEO_WIDTH=600
ID_VIDEO_HEIGHT=480
ID_VIDEO_FPS=25.000
ID_VIDEO_ASPECT=0.0000
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffh264] vfm: ffmpeg (FFmpeg H.264)
ID_VIDEO_CODEC=ffh264
Audio: no sound

Now, what is the reason for this? If I watch it on Youtube it has sound. I don’t think the sound is stripped off during download.

And why isn’t VLC playing the file at all (no video, no sound, it only shows the length of the file, but when I press the play button it stops the playback immediately).

Is somebody able to reproduce this? Or is it just me?

PS: This is the first time this happens. I have already downloaded a lot of videos with DownloadHelper.

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How did you download the file? The problem resides there, as the file might have become corrupted. –  Doktoro Reichard Sep 19 '13 at 21:24
    
I used a Firefox addon called DownloadHelper. –  erik Sep 19 '13 at 21:30
    
Instead of FLV, can you download in .mp4? I remember DownloadHelper being sketchy in the FLV department. –  Doktoro Reichard Sep 19 '13 at 21:31
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3 Answers

up vote 2 down vote accepted

Well I've tested the .mp4 (the [Medium] option on the dropdown of DownloadHelper, the .flv is taking forever though) in VLC and it went flawlessly, audio and video.

DownloadHelper does suffer some problems from then to then, so I'll check the changelog for more info on potential bugs. But the low rate of transfer of the .flv file is what signals me as the problem.

A bug report BUG 554 was opened recently and it seems it was fixed (although nothing in the bug report states completion) in version 4.9.18. I'm using the latest version.

Finally got around downloading the .flv and I don't have those problems, I can hear the sound as well as on the .mp4. My conclusion is that the addon (as described earlier) or the Internet connection botched your file.

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Ok, thanks for that hint. I downloaded the 360p webm file and it has sound and it downloads very fast. Ok, seems to be a DownloadHelper bug. I didn’t expect that. Thought that DH just downloads the files and doesn’t alter them. Maybe I was wrong with this assumption. –  erik Sep 19 '13 at 23:04
    
Remember Youtube video are actually streamed media. I would assume that, for an .flv to be downloaded, all data needed to be streamed by Youtube and simply saved. The .mp4 process might not need to actually stream the file, but I'm guessing at this point. –  Doktoro Reichard Sep 19 '13 at 23:10
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Per this site- http://www.nirsoft.net/utils/video_cache_view.html

YouTube Web site started using MPEG-DASH streams instead of flash (.flv) files. In order to convert the MPEG-DASH streams into a valid .mp4 file that can be played with any media player, you have to download and install the following open source software package: GPAC. (http://gpac.wp.mines-telecom.fr/downloads/gpac-nightly-builds/)

If you don't install the GPAC package, you'll get 2 stream files One for video and one for audio): mpegdashtmp1.mp4 and mpegdashtmp2.mp4

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If installing the package youtube-dl and running on terminal the following line produces no problems at all, the problem relies on the firefox addon itself.

vlc http://www.youtube.com/watch?v=CpznCSeqMxw --preferred-resolution 420

youtube-dl is a small command-line program to download videos from YouTube.com and a few more sites. It requires the Python interpreter (2.6, 2.7, or 3.3+), and it is not platform specific. It should work in your Unix box, in Windows or in Mac OS X. It is released to the public domain, which means you can modify it, redistribute it or use it however you like.

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