# File sink problems **URL:** \ **Category:** GNU Radio\ **Created:** [September 13, 2013, 12:30pm UTC](https://www.ruby-forum.com/t/file-sink-problems/236548 "2013-09-13T12:30:07Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![alcina](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/a587f6/32.png) [@alcina](https://www.ruby-forum.com/u/alcina)\ **Post date:** [September 13, 2013, 12:30pm UTC](https://www.ruby-forum.com/t/file-sink-problems/236548/1 "2013-09-13T12:30:07Z")
Dear all, I have simulated an OFDM transmission chain. I generated data file with 1000 samples and save it to file “random\_1k\_source”. I did ofdmmod and then ofdmdem. Finaly I saved the demodulated samples to the file “random\_1k\_sink”. I compared the files with gr\_int\_plot. The “random\_1k\_source” file has 1000 samples and the “random\_1k\_sink” file has only about 750 samples. Do I make somthing wrong? There is no difference between the file sink option unbuffered on or off. Thank for you help A. Baier ---
**Author:** ![Baier](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/77aa72/32.png) [@Baier](https://www.ruby-forum.com/u/Baier)\ **Post date:** [September 15, 2013, 7:56am UTC](https://www.ruby-forum.com/t/file-sink-problems/236548/2 "2013-09-15T07:56:16Z")
On Fri, Sep 13, 2013 at 12:27:51PM +0200, Baier wrote: > Dear all, > > I have simulated an OFDM transmission chain. I generated data file > with 1000 samples and save it to file “random\_1k\_source”. I did > ofdmmod and then ofdmdem. Finaly I saved the demodulated samples to > the file “random\_1k\_sink”. I compared the files with gr\_int\_plot. > The “random\_1k\_source” file has 1000 samples and the > “random\_1k\_sink” file has only about 750 samples. Do I make somthing > wrong? There is no difference between the file sink option > unbuffered on or off. Most likely this is connected to packet sizes (granularity of packets). Which blocks were you using? MB – Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin B. Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-43790 Fax: +49 721 608-46071 www.cel.kit.edu KIT – University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association ---
**Author:** ![Baier](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/77aa72/32.png) [@Baier](https://www.ruby-forum.com/u/Baier)\ **Post date:** [September 17, 2013, 10:49am UTC](https://www.ruby-forum.com/t/file-sink-problems/236548/3 "2013-09-17T10:49:19Z")
On Mon, Sep 16, 2013 at 09:08:53AM +0200, Baier wrote: > ``` > Most likely this is connected to packet sizes (granularity of packets). > Which blocks were you using? > > MB > > ``` > > I dont’t have any packet data transmision. I generate 1000 samples and I use > OFDM mod(fft 128, ot 100, cp 16) from GRC. It is only streaming. That still uses packets. When you increase the amount of generated data, does that help? MB – Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin B. Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-43790 Fax: +49 721 608-46071 www.cel.kit.edu KIT – University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association ---
**Author:** ![Baier](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/77aa72/32.png) [@Baier](https://www.ruby-forum.com/u/Baier)\ **Post date:** [September 18, 2013, 11:01am UTC](https://www.ruby-forum.com/t/file-sink-problems/236548/4 "2013-09-18T11:01:36Z")
On Tue, Sep 17, 2013 at 10:01:36AM +0200, Baier wrote: > If I generate 100000 samples the source file has 400 kByte and the sink file > after the ofdmmod und demod has only 95,7 kByte. > I think it could be a buffer problem. > A. B. Well yes, but it could also be a problem of packet granularity. I’m not sure how large the packets in OFDM mod are. Also, try and and remember answering to the list. MB – Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin B. Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-43790 Fax: +49 721 608-46071 www.cel.kit.edu KIT – University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association