Hey Mauro, > Thanks for all the hard work on it. Very much appreciated! > > I finally found some time to test it. For now, just a quick > test from my side, without passing any arguments to the > driver. > That's nice! > My plan is to write some patches on the top of yours, in order to > address the problems I'll find on it. If not something more critical > won't be solved in time, we may still add it at staging/media. > Let's see. OK > 3. dvbv5-zap wrote an empty audio file (without -P flag). > Probably there are still some issues at the program > channel descriptor or service; I don't remember whether I tried this. I tried dumping the stream to a file with dvbzap, which should work. By the way, I guess we should be comparing the output to this $ ffmpeg -f lavfi -i sine=frequency=1000:duration=5 -ac 2 -c:a s302m -strict -2 out.ts Since it produces a playable transport stream file that actually sounds like a sine tone. Inspecting ffmpeg & vidtv output side by side in dvbinspector, you'll see that they're mostly the same. I have a separate PID for the PCR and some other minor differences. > 4. The provider service field is null. Perhaps we could > add some string there, like "linuxtv.org". > 5. Maybe we could also add a simple NIT table, just to > avoid dvbv5-scan to wait for it until timeout. > > Also, it probably makes sense to add a debugfs interface in > order to allow injecting errors at the stream at runtime. Sure. This is fun, sign me up for it. As I said in a previous email, I think the buffer in vidtv_s302m.c is not exactly what we want. It sounds like noise. I got it from here: https://www.daycounter.com/Calculators/Sine-Generator-Calculator.phtml I will just copy what I had in a previous email here: >How do I compute the values for a sine wave such that it can be played indefinitely? > >I was thinking about this: (just spitballing here..) > >sampling_rate_khz = 48000 >buffer_size = sampling_rate_khz * seconds >i = 0 > >for i < buffer_size: >buffer[i] = 32767 * sin( 2 * PI * freq / (sampling_rate_khz * i) ) > > >but rather I want to precompute a single period for a given frequency >such that I can loop on the array indefinitely By the way, after some time trying out stuff, I guess this is actually what we need in vidtv_s302m_write_frame: static u32 vidtv_s302m_write_frame(struct vidtv_encoder *e, u16 sample) { u32 nbytes = 0; struct vidtv_s302m_frame_16 f = {}; struct vidtv_s302m_ctx *ctx = e->ctx; /* from ffmpeg: see s302enc.c */ u8 vucf = ctx->frame_index == 0 ? 1 : 0; f.data[0] = reverse[sample & 0xff]; f.data[1] = reverse[(sample & 0xff00) >> 8]; f.data[2] = (vucf << 4) | (reverse[(sample & 0x0f)] >> 4); f.data[3] = reverse[(sample & 0x0ff0) >> 4]; f.data[4] = reverse[(sample & 0xf000) >> 12] >> 4; nbytes += vidtv_memcpy(e->encoder_buf, e->encoder_buf_offset, VIDTV_S302M_BUF_SZ, &f, sizeof(f)); e->encoder_buf_offset += nbytes; ctx->frame_index++; if (ctx->frame_index >= S302M_BLOCK_SZ) ctx->frame_index = 0; return nbytes; } i.e. see: https://docplayer.net/37828038-For-television-mapping-of-aes3-data-into-an-mpeg-2-transport-stream.html Figure 5, page 4. Lastly, I am somewhat new to C, so a few things might look odd here and there. If you come across something that's too verbose tell me and I will try to tidy it up. --thanks -- Daniel
