Abstract: A method is provided for broadcasting a data stream in a network including at least two separate transmitters supplied by a head end. The stream is organized into data frames and includes at least one time marker. The method includes the following steps at the head end: obtaining a first time reference from an external source; obtaining a second time reference from the data stream received by the head end; comparing the first and second time references in order to determine a time shift between the first and second time references; and transmitting the time shift or at least one time marker modified on the basis of the time shift in order to compensate for a transport time variation between the head end and the transmitters.

Abstract: A method is provided for broadcasting a data stream in a network including at least two separate transmitters supplied by a head end. The stream is organised into data frames and includes at least one time marker. The method includes the following steps at the head end: obtaining a first time reference from an external source; obtaining a second time reference from the data stream received by the head end; comparing the first and second time references in order to determine a time shift between the first and second time references; and transmitting the time shift or at least one time marker modified on the basis of the time shift in order to compensate for a transport time variation between the head end and the transmitters.

Abstract: A method of demodulating a signal in a transmission system where the modulation includes several substantially orthogonal subcarriers, and the vector of the propagation channel H[n,k] is known or the received signal includes at least pilot symbols emitting reference data. The method includes at least one step of estimating the symbol a[n,k] emitted on the kth subcarrier of the nth symbol of the modulation using a recombination step weighting the various signals received after synchronization and demodulation x[n,k].

Abstract: The invention relates to a method of synchronizing first and second digital signals presenting digital elements to be put into correspondence, on the basis of time references. The method includes preliminary synchronization of the two digital signals using time references, by putting time references recognized as having the same value in the first and second digital signals into correspondence; and fine synchronization on the basis of a characteristic parameter obtained from the binary streams of the digital elements, and computed for each of the first and second digital signals.

Abstract: Method of demodulating a signal in a transmission system where the modulation includes several substantially orthogonal subcarriers, the vector of the propagation channel H[n,k] being known, or the received signal including at least pilot symbols emitting reference data. It comprises at least one step of estimating the symbol a[n,k] emitted on the kth subcarrier of the nth symbol of the modulation with the aid of a recombination weighting the various signals received after synchronization and demodulation x[n,k].

Abstract: The invention relates to a method of synchronizing first and second digital signals presenting digital elements to be put into correspondence, on the basis of time references.

Abstract: The invention concerns a method and a system for assessing the quality of a broadcast digital signal. A reference signal (sref) is generated (1001) from an initial signal (so) and jointly broadcast (1002) with a digital signal (sn). At reception level, the broadcast digital signal and reference signal received (snr, sref) are synchronized (2001) and a value D of the distance between the reference signal and the digital signal (snr, sref) is computed (2002) for assigning (2003) a quality value Q. The invention is applicable to the broadcast of audio and/or video digital signals.

Abstract: The invention relates to a method and to a system for measuring the quality of digital television signals comprising a data stream, the method including measuring quality and producing measurement signals that are representative of quality. The method comprises the following steps: a) selecting a reference time signal (PCR) from the data stream; b) generating a multibit digital clock signal (STC′) from the reference time signal, the phase of the clock signal being locked on the basis of the reference time signal (PCR) and its count being deduced unambiguously from the count of an initial time base (STC); and c) labelling the measurement signals with at least some of the bits (HDT) of the digital clock signal that are meaningful given the nature of the measurements performed.

Abstract: A system for broadcasting data (D) that can transmit information in the passband of a broadcast audio-frequency signal (S). The system can determine at least one frequency band (F'.sub.13, . . . , F'.sub.24) and the amplitude (A'.sub.13, . . . , A'.sub.24) of the audio-frequency signal (S). The system compares this amplitude with an auditory masking level (Nm(13), . . . , Nm(24)) associated with this frequency band and eliminates the frequency components of the audio-frequency signal in the frequency band if the amplitude of the signal is lower than the auditory masking level of the band. The system can insert the data in this frequency band at a level lower than or equal to the auditory masking level of the frequency band.